Movable body drive method and movable body drive system, pattern formation method and apparatus, exposure method and apparatus, and device manufacturing method

ABSTRACT

A controller inclines a movable body with respect to an XY plane at an angle α in a periodic direction of a grating, based on a measurement value of an interferometer which measures an angle of inclination of the movable body to the XY plane, and based on a measurement value of an encoder system and information of angle α before and after inclination, and computes an Abbe offset quantity of the grating surface with respect to a reference surface which serves as a reference for position control of the movable body in the XY plane. The controller drives the movable body, based on positional information of the movable body in the XY plane measured by the encoder system and a measurement error of the encoder system corresponding to an angle of inclination of the movable body to the XY plane due to Abbe offset quantity of the grating surface.

This is a Division of application Ser. No. 11/896,577 filed Sep. 4,2007, which claims the benefit Japanese Application No. 2006-237465filed Sep. 1, 2006. The disclosure of the prior applications is herebyincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to movable body drive methods and movablebody drive systems, pattern formation methods and apparatuses, exposuremethods and apparatuses, and device manufacturing methods, and moreparticularly to a movable body drive method in which a movable body isdriven along a predetermined plane and a movable body drive system, apattern formation method using the movable body drive method and apattern formation apparatus equipped with the movable body drive system,an exposure method using the movable body drive method and an exposureapparatus equipped with the movable body drive system, and a devicemanufacturing method in which the pattern formation method is used.

2. Description of the Background Art

Conventionally, in a lithography process for manufacturing microdevices(electron devices and the like) such as semiconductor devices and liquidcrystal display devices, exposure apparatuses such as a projectionexposure apparatus by a step-and-repeat method (a so-called stepper) anda projection exposure apparatus by a step-and-scan method (a so-calledscanning stepper (which is also called a scanner) are relativelyfrequently used.

In this kind of exposure apparatus, in order to transfer a pattern of areticle (or a mask) on a plurality of shot areas on a wafer, a waferstage holding the wafer is driven in an XY two-dimensional direction,for example, by linear motors and the like. Especially in the case of ascanning stepper, not only the wafer stage but also a reticle stage isdriven in by predetermined strokes in a scanning direction by linearmotors and the like. Position measurement of the reticle stage and thewafer stage is generally performed using a laser interferometer whosestability of measurement values is good for over a long time and has ahigh resolution.

However, requirements for a stage position control with higher precisionare increasing due to finer patterns that accompany higher integrationof semiconductor devices, and now, short-term variation of measurementvalues due to temperature fluctuation of the atmosphere on the beamoptical path of the laser interferometer has come to occupy a largepercentage in the overlay budget.

Meanwhile, as a measurement unit besides the laser interferometer usedfor position measurement of the stage, an encoder can be used, however,because the encoder uses a scale, which lacks in mechanical long-termstability (drift of grating pitch, fixed position drift, thermalexpansion and the like), it makes the encoder have a drawback of lackingmeasurement value linearity and being inferior in long-teen stabilitywhen compared with the laser interferometer.

In view of the drawbacks of the laser interferometer and the encoderdescribed above, various proposals are being made (refer to Kokai(Japanese Patent Unexamined Application Publication) No. 2002-151405bulletin, Kokai (Japanese Patent Unexamined Application Publication) No.2004-101362 bulletin and the like) of a unit that measures the positionof a stage using both a laser interferometer and an encoder (a positiondetection sensor which uses a diffraction grating) together.

Further, the measurement resolution of the conventional encoder wasinferior when compared with an interferometer, however, recently, anencoder which has a nearly equal or a better measurement resolution thana laser interferometer has appeared (for example, refer to Kokai(Japanese Patent Unexamined Application Publication) No. 2005-308592bulletin), and the technology to put the laser interferometer and theencoder described above together is beginning to gather attention.

However, for example, in the case of a projection exposure apparatus, ashot area on the wafer has to be aligned with respect to the projectionposition of the pattern on the image plane of the projection opticalsystem, but in the case of performing position measurement in themovement plane of the wafer stage that moves two-dimensionally holding awafer using an encoder, there was a risk of an error (the so-called Abbeerror) occurring in the position measurement of the wafer stage by theencoder caused by a shift of position of a scale (a grating) surfaceplaced on the wafer stage in the optical axis direction of theprojection optical system with respect to the image plane of the scale,when the wafer stage was being tilted (at the time of pitching orrolling time).

SUMMARY OF THE INVENTION

The present invention has been made in consideration of thecircumstances described above, and according to the first aspect of thepresent invention, there is provided a movable body drive method inwhich a movable body is driven along a substantially predeterminedplane, the method comprising: a drive process in which positionalinformation of the movable body in a surface parallel to the plane ismeasured using an encoder system that includes a head which irradiates ameasurement beam on a scale having a grating whose periodic direction isa predetermined direction substantially parallel to the plane andreceives a beam from the grating, wherein based on the positionalinformation and correction information of a measurement error of theencoder system due to a difference of position of a surface of the scalein a direction perpendicular to the plane with respect to a referencesurface serving as a reference for position control of the movable body,the movable body is driven along the plane.

According to this method, positional information of the movable body inthe surface parallel to the predetermined plane is measured using anencoder system, and based on the positional information and correctioninformation of the measurement error of the encoder system due to thedifference of position in a direction perpendicular to the predeterminedplane of the surface of the scale to the reference surface serving as areference for position control of the movable body, the movable body isdriven along the predetermined plane.

According to a second aspect of the present invention, there is provideda pattern formation method, comprising: a process in which an object ismounted on a movable body that can move in a movement plane; and aprocess in which the movable body is driven by the movable body drivemethod according to the movable body drive method of the presentinvention, to form a pattern to the object.

According to this method, by forming a pattern on the object mounted onthe movable body which is driven using the movable body drive method ofthe present invention, it becomes possible to form a desired pattern onthe object.

According to a third aspect of the present invention, there is provideda first device manufacturing method including a pattern formationprocess wherein in the pattern formation process, a pattern is formed onan object using the pattern formation method according to the presentinvention.

According to a fourth aspect of the present invention, there is provideda first exposure method in which a pattern is formed on an object by anirradiation of an energy beam wherein for relative movement of theenergy beam and the object, a movable body on which the object ismounted is driven, using the movable body drive method of the presentinvention.

According to this method, the movable body on which the object ismounted is driven with good precision using the movable body drivemethod of the present invention, for relative movement of the energybeam irradiated on the object and the object. Accordingly, it becomespossible to form a desired pattern on the object by scanning exposure.

According to a fifth aspect of the present invention, there is provideda second exposure method of exposing an object with an energy beamwherein the object is mounted on a movable body that can move at leastin a first and second direction orthogonal in a predetermined plane, andalso can be inclined with respect to the predetermined plane, wherebythe position of the movable body in the predetermined plane iscontrolled based on measurement information of an encoder system whichmeasures positional information of the movable body in the predeterminedplane having one of a grating section and a head unit arranged on asurface of the movable body on which the object is mounted and the otheralso arranged facing the surface of the movable body, and positionalinformation in a third direction orthogonal to the predetermined planeof a reference surface which almost coincides with the object at thetime of exposure and a grating surface of the grating section.

According to this method, it becomes possible to control the position ofthe movable body in the predetermined plane with good precision usingthe encoder system, without being affected by the measurement error ofthe encoder system due to the difference of the position in the thirddirection orthogonal to the predetermined plane of the grating surfaceof the grating section with respect to the reference surface, whichmakes it possible to expose the object on the movable body with highaccuracy.

According to a sixth aspect of the present invention, there is provideda third exposure method of exposing an object with an energy beamwherein the object is mounted on a movable body that can move at leastin a first and second direction orthogonal in a predetermined plane, andalso can be inclined with respect to the predetermined plane, wherebythe position of the movable body in the predetermined plane iscontrolled based on measurement information of an encoder system whichmeasures positional information of the movable body in the predeterminedplane having one of a grating section and a head unit arranged on asurface of the movable body on which the object is mounted and the otheralso arranged facing the surface of the movable body, and correctioninformation to compensate for the measurement error of the encodersystem that occurs due to the difference of the position in the thirddirection of the reference surface which almost coincides with theobject at the time of exposure and the grating surface of the gratingsection in a third direction orthogonal to the predetermined plane.

According to this method, it becomes possible to control the position ofthe movable body in the predetermined plane using the encoder systemwith good precision, without being affected by the measurement error ofthe encoder system that occurs due to the difference of position in thethird direction orthogonal to the predetermined plane between thereference surface and the grating surface of the grating section, whichin turn makes it possible to expose the object on the movable body withhigh precision.

According to a seventh aspect of the present invention, there isprovided a fourth exposure method of exposing an object with an energybeam wherein the object is mounted on a movable body on which a gratingsection is arranged on its surface and can be moved at least in a firstand second direction orthogonal in a predetermined plane and also can beinclined with respect to the predetermined plane in a state where theobject is almost flush with the surface, and position of the movablebody is controlled in the predetermined plane, based on measurementinformation of an encoder system that has a head unit placed facing thesurface of the movable body and measures positional information of themovable body in the predetermined plane, and correction information tocompensate for the measurement error of the encoder system that occursdue to a gap in a third direction orthogonal to the predetermined planebetween the surface of the movable body and the grating surface of thegrating section.

According to this method, it becomes possible to control the position ofthe movable body in the predetermined plane using the encoder systemwith good precision, without being affected by the measurement error ofthe encoder system that occurs due to the gap between the surface of themovable body and the grating surface of the grating section in the thirddirection orthogonal to the predetermined plane, which in turn makes itpossible to expose the object on the movable body with high precision.

According to an eighth aspect of the present invention, there isprovided a second device manufacturing method including a lithographyprocess wherein in the lithography process, a sensitive object mountedon the movable body is exposed using the exposure method according toone of the second and fourth exposure method of the present invention,and a pattern is formed on the sensitive object.

According to a ninth aspect of the present invention, there is providedmovable body drive system in which a movable body is driven along asubstantially predetermined plane, the system comprising: an encodersystem including a head that irradiates a measurement beam on a scalehaving a grating whose periodic direction is a predetermined directionsubstantially parallel to the plane and receives light from the gratingand measures positional information of the movable body in the planeparallel to the plane; and a controller which drives the movable bodyalong the plane, based on positional information of the movable body inthe predetermined direction measured by the encoder system andcorrection information of the measurement error of the encoder systemdue to the difference of the position in the direction perpendicular tothe plane of a surface of the scale with respect to a reference surfaceserving as a reference for positioning the movable body.

According to this system, the controller drives the movable body in thepredetermined plane, based on positional information of the movable bodymeasured by the encoder system in the predetermined direction parallelto the predetermined plane and the measurement error of the encodersystem according to the angle of inclination of the movable body to thepredetermined plane that occurs due to the difference of position in thedirection perpendicular to the predetermined plane of the surface of thescale with respect to the reference surface serving as a reference forposition control of the movable body. Accordingly, it becomes possibleto perform position control with high precision in the predetermineddirection parallel to the predetermined plane.

According to a tenth aspect of the present invention, there is provideda pattern formation apparatus, the apparatus comprising: a movable bodyon which the object is mounted, and is movable in a movement planeholding the object; and a movable body drive system according to thepresent invention that drives the movable body to perform patternformation on the object.

According to this apparatus, by generating a pattern on the object onthe movable body driven by the movable body drive systems of the presentinvention with a patterning unit, it becomes possible to form a desiredpattern on the object.

According to an eleventh aspect of the present invention, there isprovided a first exposure apparatus that forms a pattern on an object byan irradiation of an energy beam, the apparatus comprising: a patterningunit that irradiates the energy beam on the object; and the movable bodydrive system of the present invention whereby the movable body drivesystem drives the movable body on which the object is mounted forrelative movement of the energy beam and the object.

According to this apparatus, for relative movement of the energy beamirradiated on the object from the patterning unit and the object, themovable body on which the object is mounted is driven by the movablebody drive system of the present invention. Accordingly, it becomespossible to form a desired pattern on the object by scanning exposure.

According to a twelfth aspect of the present invention, there isprovided a second exposure apparatus that exposes an object with anenergy beam, the apparatus comprising: a movable body that holds theobject and can move at least in a first and second direction orthogonalin a predetermined plane, and also can be inclined with respect to thepredetermined plane, an encoder system which measures positionalinformation of the movable body in the predetermined plane having one ofa grating section and a head unit arranged on a surface of the movablebody on which the object is held and the other also arranged facing thesurface of the movable body, and a controller which controls theposition of the movable body in the predetermined plane, based onpositional information in a third direction orthogonal to thepredetermined plane of a reference surface which almost coincides withthe object at the time of exposure and a grating surface of the gratingsection, and measurement information of the encoder system.

According to this apparatus, it becomes possible to control the positionof the movable body in the predetermined plane with good precision usingthe encoder system, without being affected by the measurement error ofthe encoder system due to the difference of the position in the thirddirection orthogonal to the predetermined plane of the grating surfaceof the grating section with respect to the reference surface, whichmakes it possible to expose the object on the movable body with highaccuracy.

According to a thirteenth aspect of the present invention, there isprovided a third exposure apparatus that exposes an object with anenergy beam, the apparatus comprising: a movable body that holds theobject and can move at least in a first and second direction orthogonalin a predetermined plane, and also can be inclined with respect to thepredetermined plane; an encoder system which measures positionalinformation of the movable body in the predetermined plane having one ofa grating section and a head unit arranged on a surface of the movablebody on which the object is held and the other also arranged facing thesurface of the movable body; and a controller which controls theposition of the movable body in the predetermined plane, based oncorrection information to compensate for the measurement error of theencoder system that occurs due to the difference of the position in athird direction orthogonal to the predetermined plane of a referencesurface which almost coincides with the object at the time of exposureand the grating surface of the grating section, and measurementinformation of the encoder system.

According to this apparatus, it becomes possible to control the positionof the movable body in the predetermined plane using the encoder systemwith good precision, without being affected by the measurement error ofthe encoder system that occurs due to the difference of position in thethird direction orthogonal to the predetermined plane between thereference surface and the grating surface of the grating section, whichin turn makes it possible to expose the object on the movable body withhigh precision.

According to a fourteenth aspect of the present invention, there isprovided a fourth exposure apparatus that exposes an object with anenergy beam, the apparatus comprising: a movable body which can hold theobject substantially flush with a surface and also has a grating sectionarranged on the surface, and can be moved at least in the first andsecond direction which are orthogonal in a predetermined plane and canbe inclined with respect to the predetermined plane; an encoder systemwhich has a head unit placed facing the surface of the movable body, andmeasures positional information of the movable body in the predeterminedplane; and a controller which controls the position of the movable bodyin the predetermined plane, based on correction information tocompensate for the measurement error of the encoder system that occursdue to a gap in a third direction between the surface of the movablebody and the grating surface of the grating section orthogonal to thepredetermined plane and measurement information of the encoder system.

According to this apparatus, it becomes possible to control the positionof the movable body in the predetermined plane using the encoder systemwith good precision, without being affected by the measurement error ofthe encoder system that occurs due to the gap between the surface of themovable body and the grating surface of the grating section in the thirddirection orthogonal to the predetermined plane, which in turn makes itpossible to expose the object on the movable body with high precision.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings;

FIG. 1 is a view schematically showing the configuration of an exposureapparatus related to an embodiment;

FIG. 2 is a planar view showing a stage unit in FIG. 1;

FIG. 3 is a planar view showing the placement of various measuringapparatuses (such as encoders, alignment systems, a multipoint AFsystem, and Z sensors) that are equipped in the exposure apparatus inFIG. 1;

FIG. 4A is a planar view showing a wafer stage, and FIG. 4B is aschematic side view of a partially sectioned wafer stage WST;

FIG. 5A is a planar view showing a measurement stage, and FIG. 5B is aschematic side view showing a partial cross section of the measurementstage;

FIG. 6 is a block diagram showing a main configuration of a controlsystem of the exposure apparatus related to an embodiment;

FIGS. 7A and 7B are views for describing a carryover of positionmeasurement of the wafer table in the XY plane by a plurality ofencoders which respectively include a plurality of heads placed in theshape of an array and the measurement value between the heads;

FIG. 8A is a view showing an example of a configuration of an encoder,and FIG. 8B is a view used to describe a mechanism of the generation ofthis measurement error and is a view for describing a relation betweenan incident light and a diffracted light of the beam in the encoder headwith respect to the reflection grating;

FIG. 9A is a view showing a case when a count value does not change evenif a relative movement in a direction besides the measurement directionoccurs between a head of an encoder and a scale, and FIG. 9B is a viewshowing a case when a count value changes when a relative movement in adirection besides the measurement direction occurs between a head of anencoder and a scale;

FIGS. 10A to 10D are views used for describing the case when the countvalue of the encoder changes and the case when the count value does notchange, when a relative movement in a direction besides the measurementdirection occurs between the head and the scale;

FIGS. 11A and 11B are views for explaining an operation to acquirecorrection information to correct a measurement error of an encoder (afirst encoder) due to the relative movement of the head and the scale inthe non-measurement direction;

FIG. 12 is a graph showing a measurement error of the encoder withrespect to the change in the Z position in pitching amount θx=a;

FIG. 13 is a view for explaining an operation to acquire correctioninformation to correct a measurement error of another encoder (a secondencoder) due to the relative movement of the head and the scale in thenon-measurement direction;

FIG. 14 is a view for describing a calibration process of a headposition;

FIG. 15 is a view for explaining a calibration process to obtain an Abbeoffset quantity;

FIG. 16 is a view for explaining an inconvenience that occurs in thecase a plurality of measurement points on the same scale is measured bya plurality of heads;

FIG. 17 is a view for explaining a method to measure the unevenness ofthe scale (No. 1);

FIGS. 18A to 18D are views for explaining a method to measure theunevenness of the scale (No. 2);

FIG. 19 is a view for describing an acquisition operation of correctioninformation of the grating pitch of the scale and the correctioninformation of the grating deformation;

FIGS. 20A and 20B are views for explaining a concrete method to converta measurement value of the encoder that has been corrected into aposition of wafer stage WST;

FIG. 21 is a view for explaining the switching process of the encoderused for position control of the wafer stage in the XY plane;

FIG. 22 is a view conceptually showing position control of the waferstage, intake of the count value of the encoder, and an encoderswitching timing;

FIG. 23 is a view showing a state of the wafer stage and the measurementstage where exposure to a wafer on the wafer stage is performed by astep-and-scan method;

FIG. 24 is a view showing the state of both stages just after the stagesshifted from a state where the wafer stage and the measurements stageare distanced to a state where both stages are in contact after exposurehas been completed;

FIG. 25 is a view showing a state of both stages when the measurementstage is moving in a −Y direction and the wafer stage is moving towardan unloading position while keeping a positional relation between thewafer table and a measurement table in a Y-axis direction;

FIG. 26 is a view showing a state of the wafer stage and the measurementstage when the measurement stage has reached a position where a Sec-BCHK(interval) is performed;

FIG. 27 is a view showing a state of the wafer stage and the measurementstage when the wafer stage has moved from the unloading position to aloading position in parallel with the Sec-BCHK (interval) beingperformed;

FIG. 28 is a view showing a state of the wafer stage and the measurementstage when the measurement stage has moved to an optimal scrum waitingposition and a wafer has been loaded on the wafer table;

FIG. 29 is a view showing a state of both stages when the wafer stagehas moved to a position where the Pri-BCHK former process is performedwhile the measurement stage is waiting at the optimal scrum waitingposition;

FIG. 30 is a view showing a state of the wafer stage and the measurementstage when alignment marks arranged in three first alignment shot areasare being simultaneously detected using alignment systems AL1, AL2₂ andAL2₃;

FIG. 31 is a view showing a state of the wafer stage and the measurementstage when the focus calibration former process is being performed;

FIG. 32 is a view showing a state of the wafer stage and the measurementstage when alignment marks arranged in five second alignment shot areasare being simultaneously detected using alignment systems AL1 and AL2₁to AL2₄;

FIG. 33 is a view showing a state of the wafer stage and the measurementstage when at least one of the Pri-BCHK latter process and the focuscalibration latter process is being performed;

FIG. 34 is a view showing a state of the wafer stage and the measurementstage when alignment marks arranged in five third alignment shot areasare being simultaneously detected using alignment systems AL1 and AL2₁to AL2₄;

FIG. 35 is a view showing a state of the wafer stage and the measurementstage when alignment marks arranged in three fourth alignment shot areasare being simultaneously detected using alignment systems AL1, AL2₂ andAL2₃;

FIG. 36 is a view showing a state of the wafer stage and the measurementstage when the focus mapping has ended;

FIG. 37 is a flow chart for explaining an embodiment of the devicemanufacturing method; and

FIG. 38 is a flowchart used to explain a specific example of step 204 inFIG. 37.

DESCRIPTION OF THE EMBODIMENTS

An embodiment of the present invention will be described below, withreference to FIGS. 1 to 36.

FIG. 1 shows a schematic configuration of an exposure apparatus 100related to the embodiment. Exposure apparatus 100 is a scanning exposureapparatus of the step-and-scan method, namely the so-called scanner. Asit will be described later, a projection optical system PL is arrangedin the embodiment, and in the description below, a direction parallel toan optical axis AX of projection optical system PL will be described asthe Z-axis direction, a direction in a plane orthogonal to the Z-axisdirection in which a reticle and a wafer are relatively scanned will bedescribed as the Y-axis direction, a direction orthogonal to the Z-axisand the Y-axis will be described as the X-axis direction, and rotational(inclination) directions around the X-axis, the Y-axis, and the Z-axiswill be described as θx, θy, and θz directions, respectively.

Exposure apparatus 100 includes an illumination system 10, a reticlestage RST that holds a reticle R that is illuminated by an illuminationlight for exposure (hereinafter, referred to as “illumination light” or“exposure light”) IL from illumination system 10, a projection unit PUthat includes projection optical system PL that projects illuminationlight IL emitted from reticle R on a wafer W, a stage unit 50 that has awafer stage WST and a measurement stage MST, their control system, andthe like. On wafer stage WST, wafer W is mounted.

Illumination system 10 is configured including a light source, anilluminance uniformity optical system, which includes an opticalintegrator and the like, and n illumination optical system that has areticle blind and the like (none of which are shown), as is disclosedin, for example, Kokai (Japanese Patent Unexamined ApplicationPublication) No. 2001-313250 bulletin (the corresponding U.S. PatentApplication Publication No. 2003/0025890 description) and the like. Inillumination system 10, a slit-shaped illumination area extending in theX-axis direction which is set on reticle R with a reticle blind (amasking system) is illuminated by illumination light (exposure light) ILwith a substantially uniform illuminance. In this case, as illuminationlight IL, for example, an ArF excimer laser beam (wavelength 193 nm) isused. Further, as the optical integrator, for example, a fly-eye lens, arod integrator (an internal reflection type integrator), a diffractiveoptical element or the like can be used.

On reticle stage RST, reticle R on which a circuit pattern or the likeis formed on its pattern surface (the lower surface in FIG. 1) is fixed,for example, by vacuum chucking. Reticle stage RST is finely drivable ormovable in within an XY plane by a reticle stage drive section 11 (notshown in FIG. 1, refer to FIG. 6) that includes a linear motor or thelike, and reticle stage RST is also drivable in a predetermined scanningdirection (in this case, the Y-axis direction, which is the lateraldirection of the page surface in FIG. 1) at a designated scanning speed.

The positional information (including rotation information in the θzdirection) of reticle stage RST in the movement plane is constantlydetected, for example, at a resolution of around 0.5 to 1 nm by areticle laser interferometer (hereinafter referred to as a “reticleinterferometer”) 116, via a movable mirror 15 (the mirrors actuallyarranged are a Y movable mirror that has a reflection surface which isorthogonal to the Y-axis direction and an X movable mirror that has areflection surface orthogonal to the X-axis direction). The measurementvalues of reticle interferometer 116 are sent to a main controller 20(not shown in FIG. 1, refer to FIG. 6). Main controller 20 computes theposition of reticle stage RST in the X-axis direction, Y-axis direction,and the θz direction based on the measurement values of reticleinterferometer 116, and also controls the position (and velocity) ofreticle stage RST by controlling reticle stage drive section 11 based onthe computation results. Incidentally, instead of movable mirror 15, theedge surface of reticle stage RSV can be mirror polished so as to form areflection surface (corresponding to the reflection surface of movablemirror 15). Further, reticle interferometer 116 can measure positionalinformation of reticle stage RST related to at least one of the Z-axis,θx, or θy directions.

Projection unit PU is placed below reticle stage RST in FIG. 1.Projection unit PU includes a barrel 40, and projection optical systemPL that has a plurality of optical elements which are held in apredetermined positional relation inside barrel 40. As projectionoptical system PL, for example, a dioptric system is used, consisting ofa plurality of lenses (lens elements) that is disposed along an opticalaxis AX, which is parallel to the Z-axis direction. Projection opticalsystem PL is, for example, a both-side telecentric dioptric system thathas a predetermined projection magnification (such as one-quarter,one-fifth, or one-eighth times). Therefore, when illumination light ILfrom illumination system 10 illuminates illumination area IAR, a reducedimage of the circuit pattern (a reduced image of a part of the circuitpattern) of the reticle is formed within illumination area IAR, withillumination light IL that has passed through reticle R which is placedso that its pattern surface substantially coincides with a first plane(an object plane) of projection optical system PL, in an area conjugateto illumination area IAR on wafer W (exposure area) whose surface iscoated with a resist (a sensitive agent) and is placed on a second plane(an image plane) side, via projection optical system PL (projection unitPU) and liquid Lq (refer to FIG. 1). And by reticle stage RST and waferstage WST being synchronously driven, the reticle is relatively moved inthe scanning direction (the Y-axis direction) with respect toillumination area IAR (illumination light IL) while wafer W isrelatively moved in the scanning direction (the Y-axis direction) withrespect to the exposure area (illumination light IL), thus scanningexposure of a shot area (divided area) on wafer W is performed, and thepattern of the reticle is transferred onto the shot area. That is, inthe embodiment, the pattern is generated on wafer W according toillumination system 10, the reticle, and projection optical system PL,and then by the exposure of the sensitive layer (resist layer) on waferW with illumination light IL, the pattern is formed on wafer W. Althoughit is not shown in the drawings, projection unit PU is mounted on abarrel platform supported by three struts via a vibration isolationmechanism, however, as is disclosed in, for example, the pamphlet ofInternational Publication No. WO 2006/038952 and the like, projectionunit PU can be supported by suspension with respect to a mainframemember (not shown) placed above projection unit PU or with respect to abase member on which reticle stage RST is placed.

Further, in exposure apparatus 100 of the embodiment, in order toperform exposure applying the liquid immersion method, a nozzle unit 32that constitutes part of a local liquid immersion unit 8 is arranged soas to enclose the periphery of the lower end portion of barrel 40 thatholds an optical element that is closest to an image plane side (wafer Wside) that constitutes projection optical system PL, which is a lens(hereinafter, also referred to a “tip lens”) 191 in this case. In theembodiment, as shown in FIG. 1, the lower end surface of nozzle unit 32is set to be substantially flush with the lower end surface of tip lens191. Further, nozzle unit 32 is equipped with a supply opening and arecovery opening of liquid Lq, a lower surface to which wafer W isplaced facing and at which the recovery opening is arranged, and asupply flow channel and a recovery flow channel that are connected to aliquid supply pipe 31A and a liquid recovery pipe 31B respectively. Asshown in FIG. 3, liquid supply pipe 31A and liquid recovery pipe 31B areinclined at an angle of 45 degrees with respect to the X-axis directionand the Y-axis direction in a planer view (when viewed from above) andare symmetrically placed with respect to a straight line LV in theY-axis direction that passes through optical axis AX of projectionoptical system PL.

One end of a supply pipe (not shown) is connected to liquid supply pipe31A while the other end of the supply pipe is connected to a liquidsupply unit 5 (not shown in FIG. 1, refer to FIG. 6), and one end of arecovery pipe (not shown) is connected to liquid recovery pipe 31B whilethe other end of the recovery pipe is connected to a liquid recoveryunit 6 (not shown in FIG. 1, refer to FIG. 6).

Liquid supply unit 5 includes a liquid tank, a compression pump, atemperature controller, a valve for controlling supply/stop of theliquid to liquid supply pipe 31A, and the like. As the valve, forexample, a flow rate control valve is preferably used so that not onlythe supply/stop of the liquid but also the adjustment of flow rate canbe performed. The temperature controller adjusts the temperature of theliquid within the liquid tank to nearly the same temperature, forexample, as the temperature within the chamber (not shown) where theexposure apparatus is housed. Incidentally, the tank for supplying theliquid, the compression pump, the temperature controller, the valve, andthe like do not all have to be equipped in exposure apparatus 100, andat least part of them can also be substituted by the equipment or thelike available in the plant where exposure apparatus 100 is installed.

Liquid recovery unit 6 includes a liquid tank, a suction pump, a valvefor controlling recovery/stop of the liquid via liquid recovery pipe31B, and the like. As the valve, a flow rate control valve is preferablyused corresponding to the valve of liquid supply unit 5. Incidentally,the tank for recovering the liquid, the suction pump, the valve, and thelike do not all have to be equipped in exposure apparatus 100, and atleast part of them can also be substituted by the equipment or the likeavailable in the plant where exposure apparatus 100 is installed.

In the embodiment, as the liquid described above, pure water(hereinafter, it will simply be referred to as “water” besides the casewhen specifying is necessary) that transmits the ArF excimer laser light(light with a wavelength of 193 nm) is to be used. Pure water can beobtained in large quantities at a semiconductor manufacturing plant orthe like without difficulty, and it also has an advantage of having noadverse effect on the photoresist on the wafer, to the optical lenses orthe like.

Refractive index n of the water with respect to the ArF excimer laserlight is around 1.44. In the water the wavelength of illumination lightIL is 193 nm×1/n, shorted to around 134 nm.

Liquid supply unit 5 and liquid recovery unit 6 each have a controller,and the respective controllers are controlled by main controller 20(refer to FIG. 6). According to instructions from main controller 20,the controller of liquid supply unit 5 opens the valve connected toliquid supply pipe 31A to a predetermined degree to supply water Lq(refer to FIG. 1) to the space between tip lens 191 and wafer W vialiquid supply pipe 31A, the supply flow channel and the supply opening.Further, when the water is supplied, according to instructions from maincontroller 20, the controller of liquid recovery unit 6 opens the valveconnected to liquid recovery pipe 31B to a predetermined degree torecover water Lq from the space between tip lens 191 and wafer W intoliquid recovery unit 6 (the liquid tank) via the recovery opening, therecovery flow channel and liquid recovery pipe 31B. During the supplyand recovery operations, main controller 20 gives commands to thecontrollers of liquid supply unit 5 and liquid recovery unit 6 so thatthe quantity of water supplied to the space between tip lens 191 andwafer W constantly equals the quantity of water recovered from thespace. Accordingly, a constant quantity of water Lq is held (refer toFIG. 1) in the space between tip lens 191 and wafer W. In this case,water Lq held in the space between tip lens 191 and wafer W isconstantly replaced.

As is obvious from the above description, in the embodiment, localliquid immersion unit 8 is configured including nozzle unit 32, liquidsupply unit 5, liquid recovery unit 6, liquid supply pipe 31A and liquidrecovery pipe 31B, and the like. Local liquid immersion unit 8 fillsliquid Lq in the space between tip lens 191 and wafer W by nozzle unit32, so that a local liquid immersion space (equivalent to a liquidimmersion area 14) which includes the optical path space of illuminationlight IL is formed. Accordingly, nozzle unit 32 is also called a liquidimmersion space formation member or a containment member (or, aconfinement member). Incidentally, part of local liquid immersion unit8, for example, at least nozzle unit 32 may also be supported in asuspended state by a main frame (including the barrel platform) thatholds projection unit PU, or may also be arranged at another framemember that is separate from the main frame. Or, in the case projectionunit PU is supported in a suspended state as is described earlier,nozzle unit 32 may also be supported in a suspended state integrallywith projection unit PU, but in the embodiment, nozzle unit 32 isarranged on a measurement frame that is supported in a suspended stateindependently from projection unit PU. In this case, projection unit PUdoes not have to be supported in a suspended state.

Incidentally, also in the case measurement stage MST is located belowprojection unit PU, the space between a measurement table (to bedescribed later) and tip lens 191 can be filled with water in a similarmanner to the manner described above.

Incidentally, in the description above, one liquid supply pipe (nozzle)and one liquid recovery pipe (nozzle) were arranged as an example,however, the present invention is not limited to this, and aconfiguration having multiple nozzles as is disclosed in, for example,the pamphlet of International Publication No. WO 99/49504, may also beemployed, in the case such an arrangement is possible taking intoconsideration a relation with adjacent members. Further, the lowersurface of nozzle unit 32 can be placed near the image plane (morespecifically, a wafer) of projection optical system PL rather than theoutgoing plane of tip lens 191, or, in addition to the optical path ofthe image plane side of tip lens 191, a configuration in which theoptical path on the object plane side of tip lens 191 is also filledwith liquid can be employed. The point is that any configuration can beemployed, as long as the liquid can be supplied in the space betweenoptical member (tip lens) 191 in the lowest end constituting projectionoptical system PL and wafer W. For example, the liquid immersionmechanism disclosed in the pamphlet of International Publication No. WO2004/053955, or the liquid immersion mechanism disclosed in the EPPatent Application Publication No. 1 420 298 description can also beapplied to the exposure apparatus of the embodiment.

Referring back to FIG. 1, stage unit 50 is equipped with wafer stage WSTand measurement stage MST that are placed above a base board 12, aninterferometer system 118 (refer to FIG. 6) including Y interferometers16 and 18 that measure position information of stages WST and MST, anencoder system (to be described later) that is used for measuringposition information of wafer stage WST on exposure or the like, a stagedrive system 124 (refer to FIG. 6) that drives stages WST and MST, andthe like.

On the bottom surface of each of wafer stage WST and measurement stageMST, a noncontact bearing (not shown), for example, a vacuum preloadtype hydrostatic air bearing (hereinafter, referred to as an “air pad”)is arranged at a plurality of points. Wafer stage WST and measurementstage MST are supported in a noncontact manner via a clearance of aroundseveral μm above base board 12, by static pressure of pressurized airthat is blown out from the air pad toward the upper surface of baseboard 12. Further, stages WST and MST are independently drivable intwo-dimensional directions, which are the Y-axis direction (a horizontaldirection of the page surface of FIG. 1) and the X-axis direction (anorthogonal direction to the page surface of FIG. 1) in a predeterminedplane (the XY plane), by stage drive system 124.

To be more specific, on a floor surface, as shown in the planar view inFIG. 2, a pair of Y-axis stators 86 and 87 extending in the Y-axisdirection are respectively placed on one side and the other side in theX-axis direction with base board 12 in between. Y-axis stators 86 and 87are each composed of, for example, a magnetic pole unit thatincorporates a permanent magnet group that is made up of a plurality ofsets of a north pole magnet and a south pole magnet that are placed at apredetermined distance and alternately along the Y-axis direction. AtY-axis stators 86 and 87, two Y-axis movers 82 and 84, and two Y-axismovers 83 and 85 are respectively arranged in a noncontact engagedstate. In other words, four Y-axis movers 82, 84, 83 and 85 in total arein a state of being inserted in the inner space of Y-axis stator 86 or87 whose XZ sectional surface has a U-like shape, and are severallysupported in a noncontact manner via a clearance of for example, aroundseveral μm via the air pad (not shown) with respect to correspondingY-axis stator 86 or 87. Each of Y-axis movers 82, 84, 83 and 85 iscomposed of, for example, an armature unit that incorporates armaturecoils placed at a predetermined distance along the Y-axis direction.That is, in the embodiment, Y-axis movers 82 and 84 made up of thearmature units and Y-axis stator 86 made up of the magnetic pole unitconstitute moving coil type Y-axis linear motors respectively.Similarly, Y-axis movers 83 and 85 and Y-axis stator 87 constitutemoving coil type Y-axis linear motors respectively. In the followingdescription, each of the four Y-axis linear motors described above isreferred to as a Y-axis linear motor 82, a Y-axis linear motor 84, aY-axis linear motor 83 and a Y-axis linear motor 85 as needed, using thesame reference codes as their movers 82, 84, 83 and 85.

Movers 82 and 83 of two Y-axis linear motors 82 and 83 out of the fourY-axis linear motors are respectively fixed to one end and the other endin a longitudinal direction of an X-axis stator 80 that extends in theX-axis direction. Further, movers 84 and 85 of the remaining two Y-axislinear motors 84 and 85 are fixed to one end and the other end of anX-axis stator 81 that extends in the X-axis direction. Accordingly,X-axis stators 80 and 81 are driven along the Y-axis by a pair of Y-axislinear motors 82 and 83 and a pair of Y-axis linear motors 84 and 85respectively.

Each of X-axis stators 80 and 81 is composed of, for example, anarmature unit that incorporates armature coils placed at a predetermineddistance along the X-axis direction.

One X-axis stator, X-axis stator 81 is arranged in a state of beinginserted in an opening (not shown) formed at a stage main section 91(not shown in FIG. 2, refer to FIG. 1) that constitutes part of waferstage WST. Inside the opening of stage main section 91, for example, amagnetic pole unit, which has a permanent magnet group that is made upof a plurality of sets of a north pole magnet and a south pole magnetplaced at a predetermined distance and alternately along the X-axisdirection, is arranged. This magnetic pole unit and X-axis stator 81constitute a moving magnet type X-axis linear motor that drives stagemain section 91 in the X-axis direction. Similarly, the other X-axisstator, X-axis stator 80 is arranged in a state of being inserted in anopening formed at a stage main section 92 (not shown in FIG. 2, refer toFIG. 1) that constitutes part of measurement stage MST. Inside theopening of stage main section 92, a magnetic pole unit, which is similarto the magnetic pole unit on the wafer stage WST side (stage mainsection 91 side), is arranged. This magnetic pole unit and X-axis stator80 constitute a moving magnet type X-axis linear motor that drivesmeasurement stage MST in the X-axis direction.

In the embodiment, each of the linear motors described above thatconstitute stage drive system 124 is controlled by main controller 20shown in FIG. 6. Incidentally, each linear motor is not limited toeither one of the moving magnet type or the moving coil type, and thetypes can appropriately be selected as needed.

Incidentally, by making thrust forces severally generated by a pair ofY-axis linear motors 84 and 85 be slightly different, yawing (rotationquantity in the Δz direction) of wafer stage WST can be controlled.Further, by making thrust forces severally generated by a pair of Y-axislinear motors 82 and 83 be slightly different, yawing of measurementstage MST can be controlled.

Referring back to FIG. 1, Wafer stage WST includes stage main section 91previously described and a wafer table WTB that is mounted on stage mainsection 91. Wafer table WTB and stage main section 91 are finely drivenrelative to base board 12 and X-axis stator 81 in the Z-axis direction,the θx direction, and the θy direction by a Z leveling mechanism (notshown) (including, for example, a voice coil motor and the like). Morespecifically, wafer table WTB is finely movable in the Z-axis directionand can also be inclined (tilted) with respect to the XY plane (or theimage plane of projection optical system PL). Incidentally, in FIG. 6,stage drive system 124 is shown including each of the linear motors andthe Z-leveling mechanism described above. Further, wafer table WTB canalso be configured finely movable in at least one of the X-axis, theY-axis, and the θz directions.

On wafer table WTB, a wafer holder (not shown) that holds wafer W byvacuum suction or the like is arranged. The wafer holder may also beformed integrally with wafer table WTB, but in the embodiment, the waferholder and wafer table WTB are separately configured, and the waferholder is fixed inside a recessed portion of wafer table WTB, forexample, by vacuum suction or the like. Further, on the upper surface ofwafer table WTB, a plate (liquid repellent plate) 28 is arranged, whichhas the surface (liquid repellent surface) substantially flush with thesurface of a wafer mounted on the wafer holder to which liquid repellentprocessing with respect to liquid Lq is performed, has a rectangularouter shape (contour), and has a circular opening that is formed in thecenter portion and is slightly larger than the wafer holder (a mountingarea of the wafer). Plate 28 is made of materials with a low coefficientof thermal expansion, such as glasses or ceramics (such as Zerodur (thebrand name) of Schott AG, Al₂O₃, or TiC), and on the surface of plate28, a liquid repellent film is formed by, for example, fluorine resinmaterials, fluorine series resin materials such aspolytetrafluoroethylene (Teflon (registered trademark)), acrylic resinmaterials, or silicon series resin materials. Further, as shown in aplaner view of wafer table WTB (wafer stage WST) in FIG. 4A, plate 28has a first liquid repellent area 28 a whose outer shape (contour) isrectangular enclosing a circular opening, and a second liquid repellentarea 28 b that has a rectangular frame (annular) shape placed around thefirst liquid repellent area 28 a. On the first liquid repellent area 28a, for example, at the time of an exposure operation, at least part of aliquid immersion area 14 that is protruded from the surface of the waferis formed, and on the second liquid repellent area 28 b, scales for anencoder system (to be described later) are formed. Incidentally, atleast part of the surface of plate 28 does not have to be flush with thesurface of the wafer, that is, may have a different height from that ofthe surface of the wafer. Further, plate 28 may be a single plate, butin the embodiment, plate 28 is configured by combining a plurality ofplates, for example, first and second liquid repellent plates thatcorrespond to the first liquid repellent area 28 a and the second liquidrepellent area 28 b respectively. In the embodiment, pure water is usedas liquid Lq as is described above, and therefore, hereinafter the firstliquid repellent area 28 a and the second liquid repellent area 28 b arealso referred to as a first water repellent plate 28 a and a secondwater repellent plate 28 b.

In this case, exposure light IL is irradiated to the first waterrepellent plate 28 a on the inner side, while exposure light IL ishardly irradiated to the second water repellent plate 28 b on the outerside. Taking this fact into consideration, in the embodiment, a firstwater repellent area to which water repellent coat having sufficientresistance to exposure light IL (light in a vacuum ultraviolet region,in this case) is applied is formed on the surface of the first waterrepellent plate 28 a, and a second water repellent area to which waterrepellent coat having resistance to exposure light IL inferior to thefirst water repellent area is applied is formed on the surface of thesecond water repellent plate 28 b. In general, since it is difficult toapply water repellent coat having sufficient resistance to exposurelight IL (light in a vacuum ultraviolet region, in this case) to a glassplate, it is effective to separate the water repellent plate into twosections in this manner, i.e. the first water repellent plate 28 a andthe second water repellent plate 28 b around it. Incidentally, thepresent invention is not limited to this, and two types of waterrepellent coat that have different resistance to exposure light IL mayalso be applied on the upper surface of the same plate in order to formthe first water repellent area and the second water repellent area.Further, the same kind of water repellent coat may be applied to thefirst and second water repellent areas. For example, only one waterrepellent area may also be formed on the same plate.

Further, as is obvious from FIG. 4A, at the end portion on the +Y sideof the first water repellent plate 28 a, a rectangular cutout is formedin the center portion in the X-axis direction, and a measurement plate30 is embedded inside the rectangular space (inside the cutout) that isenclosed by the cutout and the second water repellent plate 28 b. Afiducial mark FM is formed in the center in the longitudinal directionof measurement plate 30 (on a centerline LL of wafer table WTB), and apair of aerial image measurement slit patterns (slit-shaped measurementpatterns) SL are formed in a symmetrical placement with respect to thecenter of fiducial mark FM on one side and the other side in the X-axisdirection of fiducial mark FM. As each of aerial image measurement slitpatterns SL, an L-shaped slit pattern having sides along the Y-axisdirection and X-axis direction can be used, as an example.

Further, as shown in FIG. 4B, at the wafer stage WST section below eachof aerial image measurement slit patterns SL, an L-shaped housing 36 inwhich an optical system containing an objective lens, a mirror, a relaylens and the like is housed is attached in a partially embedded statepenetrating through part of the inside of wafer table WTB and stage mainsection 91. Housing 36 is arranged in pairs corresponding to the pair ofaerial image measurement slit patterns SL, although omitted in thedrawing.

The optical system inside housing 36 guides illumination light IL thathas been transmitted through aerial image measurement slit pattern SLalong an L-shaped route and emits the light toward a −Y direction.Incidentally, in the following description, the optical system insidehousing 36 is described as a light-transmitting system 36 by using thesame reference code as housing 36 for the sake of convenience.

Moreover, on the upper surface of the second water repellent plate 28 b,multiple grid lines are directly formed in a predetermine pitch alongeach of four sides. More specifically, in areas on one side and theother side in the X-axis direction of the second water repellent plate28 b (both sides in the horizontal direction in FIG. 4A), Y scales 39Y₁and 39Y₂ are formed, respectively. Y scales 39Y₁ and 39Y₂ are eachcomposed of a reflective grating (e.g. diffraction grating) having aperiodic direction in the Y-axis direction in which grid lines 38 havingthe longitudinal direction in the X-axis direction are formed in apredetermined pitch along a direction parallel to the Y-axis (Y-axisdirection).

Similarly, in areas on one side and the other side in the Y-axisdirection of the second water repellent plate 28 b (both sides in thevertical direction in FIG. 4A), X scales 39X₁ and 39X₂ are formedrespectively. X scales 39X₁ and 39X₂ are each composed of a reflectivegrating (e.g. diffraction grating) having a periodic direction in theX-axis direction in which grid lines 37 having the longitudinaldirection in the Y-axis direction are formed in a predetermined pitchalong a direction parallel to the X-axis (X-axis direction). As each ofthe scales, the scale made up of a reflective diffraction grating RG(refer to FIG. 8) that is created by, for example, hologram or the likeon the surface of the second water repellent plate 28 b is used. In thiscase, each scale has gratings made up of narrow slits, grooves or thelike that are marked at a predetermined distance (pitch) as graduations.The type of diffraction grating used for each scale is not limited, andnot only the diffraction grating made up of grooves or the like that aremechanically formed, but also, for example, the diffraction grating thatis created by exposing interference fringe on a photosensitive resin maybe used. However, each scale is created by marking the graduations ofthe diffraction grating, for example, in a pitch between 138 nm to 4 μm,for example, a pitch of 1 μm on a thin plate shaped glass. These scalesare covered with the liquid repellent film (water repellent film)described above. Incidentally, the pitch of the grating is shown muchwider in FIG. 4A than the actual pitch, for the sake of convenience. Thesame is true also in other drawings.

In this manner, in the embodiment, since the second water repellentplate 28 b itself constitutes the scales, a glass plate with low-thermalexpansion is to be used as the second water repellent plate 28 b.However, the present invention is not limited to this, and a scalemember made up of a glass plate or the like with low-thermal expansionon which a grating is formed may also be fixed on the upper surface ofwafer table WTB, by a plate spring (or vacuum suction) or the like so asto prevent local shrinkage/expansion. In this case, a water repellentplate to which the same water repellent coat is applied on the entiresurface may be used instead of plate 28. Or, wafer table WTB may also beformed by a low thermal expansion material, and in such a case, a pairof Y scales and a pair of X scales may be directly formed on the uppersurface of wafer table WTB.

Incidentally, in order to protect the diffraction grating, it is alsoeffective to cover the grating with a glass plate with low thermalexpansion that has liquid repellency. In this case, the thickness of theglass plate, for example, is 1 mm, and the glass plate is set on theupper surface of the wafer table WST so that its surface is at the sameheight same as the wafer surface. Therefore, the distance between thesurface (substantially flush with the upper surface of wafer stage WSTin the embodiment) of wafer W held (mounted) on wafer stage WST and thegrating surface of the scale in the Z-axis direction is to be 1 mm.

Incidentally, a lay out pattern is arranged for deciding the relativeposition between an encoder head and a scale near the edge of the scale(to be described later). The lay out pattern is configured from gridlines that have different reflectivity, and when the encoder head scansthe pattern, the intensity of the output signal of the encoder changes.Therefore, a threshold value is determined beforehand, and the positionwhere the intensity of the output signal exceeds the threshold value isdetected. Then, the relative position between the encoder head and thescale is set, with the detected position as a reference.

In the embodiment, main controller 20 can obtain the displacement ofwafer stage WST in directions of six degrees of freedom (the Z, X, Y,θz, θx, and θy directions) in the entire stroke area from themeasurement results of interferometer system 118 (refer to FIG. 6). Inthis case, interferometer system 118 includes X interferometers 126 to128, Y interferometer 16, and Z interferometers 43A and 43B.

To the −Y edge surface and the −X edge surface of wafer table WTB,mirror-polishing is applied, respectively, and a reflection surface 17 aand a reflection surface 17 b shown in FIG. 2 are formed. By severallyprojecting an interferometer beam (measurement beam) to reflectionsurface 17 a and reflection surface 17 b and receiving a reflected lightof each beam, Y interferometer 16 and X interferometers 126, 127, and128 (X interferometers 126 to 128 are not shown in FIG. 1, refer to FIG.2) of interferometer system 118 (refer to FIG. 6) measure a displacementof each reflection surface from a datum position (generally, a fixedmirror is placed on the side surface of projection unit PU, and thesurface is used as a reference surface), that is, positional informationof wafer stage WST within the XY plane, and the measurement values aresupplied to main controller 20. In the embodiment, as it will bedescribed later on, as each interferometer a multiaxial interferometerthat has a plurality of measurement axes is used with an exception for apart of the interferometers.

Meanwhile, to the side surface on the −Y side of stage main section 91,a movable mirror 41 having the longitudinal direction in the X-axisdirection is attached via a kinematic support mechanism (not shown), asshown in FIGS. 1 and 4B.

A pair of Z interferometers 43A and 43B (refer to FIGS. 1 and 2) thatconfigures a part of interferometer system 118 (refer to FIG. 6) andirradiates measurement beams on movable mirror 41 is arranged facingmovable mirror 41. To be more specific, as it can be seen when viewingFIGS. 2 and 4B together, movable mirror 41 is designed so that thelength in the X-axis direction is longer than reflection surface 17 a ofwafer table WTB by at least the interval of Z interferometers 43A and43B. Further, movable mirror 41 is composed of a member having ahexagonal cross-section shape as in a rectangle and an isoscelestrapezoid that has been integrated. Mirror-polishing is applied to thesurface on the −Y side of movable mirror 41, and three reflectionsurfaces 41 b, 41 a, and 41 c are formed.

Reflection surface 41 a configures the edge surface on the −Y side ofmovable mirror 41, and reflection surface 41 a is parallel with the XZplane and also extends in the X-axis direction. Reflection surface 41 bconfigures a surface adjacent to the +Z side of reflection surface 41 a,and reflection surface 41 b is parallel with a plane inclined in aclockwise direction in FIG. 4B at a predetermined angle with respect tothe XZ plane and also extends in the X-axis direction. Reflectionsurface 41 c configures a surface adjacent to the −Z side of reflectionsurface 41 a, and is arranged symmetrically with reflection surface 41b, with reflection surface 41 b in between.

As it can be seen when viewing FIGS. 1 and 2 together, Z interferometers43A and 43B are placed apart on one side and the other side of Yinterferometer 16 in the X-axis direction at a substantially equaldistance and at positions slightly lower than Y interferometer 16,respectively.

From each of the Z interferometers 43A and 43B, as shown in FIG. 1,measurement beam B1 along the Y-axis direction is projected towardreflection surface 41 b, and measurement beam B2 along the Y-axisdirection is projected toward reflection surface 41 c (refer to FIG.4B). In the embodiment, fixed mirror 47A having a reflection surfaceorthogonal to measurement beam B1 reflected off reflection surface 41 band a fixed mirror 47B having a reflection surface orthogonal tomeasurement beam B2 reflected off reflection surface 41 c are arranged,each extending in the X-axis direction at a position distanced apartfrom movable mirror 41 in the −Y-direction by a predetermined distancein a state where the fixed mirrors do not interfere with measurementbeams B1 and B2.

Fixed mirrors 47A and 47B are supported, for example, by the samesupport body (not shown) arranged in the frame (not shown) whichsupports projection unit PU. Incidentally, fixed mirrors 47A and 47B canbe arranged in the measurement frame or the like previously described.Further, in the embodiment, movable mirror 41 having three reflectionsurfaces 41 b, 41 a, and 41 c and fixed mirrors 47A and 47B werearranged, however, the present invention is not limited to this, and forexample, a configuration in which a movable mirror having an inclinedsurface of 45 degrees is arranged on the side surface of stage mainsection 91 and a fixed mirror is placed above wafer stage WST can beemployed. In this case, the fixed mirror can be arranged in the supportbody previously described or in the measurement frame.

Y interferometer 16, as shown in FIG. 2, projects measurement beams B4₁and B4₂ on reflection surface 17 a of wafer table WTB along ameasurement axis in the Y-axis direction spaced apart by an equaldistance to the −X side and the +X side from a straight line that isparallel to the Y-axis which passes through the projection center(optical axis AX, refer to FIG. 1) of projection optical system PL, andby receiving each reflected light, detects the position of wafer tableWTB in the Y-axis direction (a Y position) at the irradiation point ofmeasurement beams B4₁ and B4₂. Incidentally, in FIG. 1, measurementbeams B4₁ and B4₂ are representatively shown as measurement beam B4.

Further, Y interferometer 16 projects a measurement beam B3 towardreflection surface 41 a along a measurement axis in the Y-axis directionwith a predetermined distance in the Z-axis direction spaced betweenmeasurement beams B4₁ and B4₂, and by receiving measurement beam B3reflected off reflection surface 41 a, detects the Y position ofreflection surface 41 a (more specifically wafer stage WST) of movablemirror 41.

Further, main controller 20 computes displacement (yawing amount)Δθz^((Y)) in the θz direction of wafer table WTB, based on a differenceof the measurement values of the measurement axes corresponding tomeasurement beams B4₁ and B4₂. Further, main controller 20 computesdisplacement (pitching amount) Δθx in the θx direction of wafer stageWST, based on the Y position (displacement ΔY in the Y-axis direction)in reflection surface 17 a and reflection surface 41 a.

Further, as shown in FIG. 2, X interferometer 126 projects measurementbeams B5₁ and B5₂ on wafer table WTB along the dual measurement axesspaced apart from straight line LH in the X-axis direction that passesthe optical axis of projection optical system PL by the same distance,and based on the measurement values of the measurement axescorresponding to measurement beams B5₁ and B5₂, main controller 20computes a position (an X position, or to be more precise, displacementAX in the X-axis direction) of wafer table WTB in the X-axis direction.Further, main controller 20 computes displacement (yawing amount)Δθz^((X)) of wafer table WTB in the θz direction from a difference ofthe measurement values of the measurement axes corresponding tomeasurement beams B5₁ and B5₂. Incidentally, Δθz^((X)) obtained from Xinterferometer 126 and Δθz^((Y)) obtained from Y interferometer 16 areequal to each other, and represents displacement (yawing amount) Δθz ofwafer table WTB in the θz direction.

Further, as is indicated in a dotted line in FIG. 2, a measurement beamB7 is emitted from X interferometer 128 along a measurement axisparallel to the X-axis. X interferometer 128 actually projectsmeasurement beam B7 on reflection surface 17 b of wafer table WTBlocated in the vicinity of an unloading position UP and a loadingposition LP along a measurement axis, which is parallel to the X-axisand joins unloading position UP and loading position LP (refer to FIG.3) as in the description later on. Further, as shown in FIG. 2, ameasurement beam B6 from X interferometer 127 is projected on reflectionsurface 17 b of wafer table WTB. Measurement beam B6 is actuallyprojected on reflection surface 17 b of wafer table WTB along ameasurement axis parallel to the X-axis that passes through thedetection center of a primary alignment system AL1.

Main controller 20 can obtain displacement ΔX of wafer table WTB in theX-axis direction from the measurement values of length measurement beamB6 of X interferometer 127 and the measurement values of lengthmeasurement beam B7 of X interferometer 128. However, the three Xinterferometers 126, 127, and 128 are placed differently regarding theY-axis direction, and X interferometer 126 is used at the time ofexposure as shown in FIG. 22, X interferometer 127 is used at the timeof wafer alignment as shown in FIG. 29 and the like, and Xinterferometer 128 is used at the time of wafer loading shown in FIGS.26 and 27 and wafer unloading shown in FIG. 25.

Further from Z interferometers 43A and 43B, measurement beams B1 and B2that proceed along the Y-axis are projected toward movable mirror 41,respectively. These measurement beams B1 and B2 are incident onreflection surfaces 41 b and 41 c of movable mirror 41, respectively, ata predetermined angle of incidence (the angle is to be θ/2). Then,measurement beams B1 and B2 are reflected off reflection surfaces 41 band 41 c, respectively, and are incident on the reflection surfaces offixed mirrors 47A and 47B perpendicularly. Then, measurement beams B1and B2, which were reflected off the reflection surface of fixed mirrors47A and 47B, are reflected off reflection surfaces 41 b and 41 c again(returns the optical path at the time of incidence), respectively, andare received by Z interferometers 43A and 43B.

In this case, when displacement of wafer stage WST (more specificallymovable mirror 41) in the Y-axis direction is ΔYo and displacement inthe Z-axis direction is ΔZo, an optical path length change ΔL1 ofmeasurement beam B1 and an optical path length change ΔL2 of measurementbeam B2 received at of Z interferometers 43A and 43B can respectively beexpressed as in formulas (1) and (2) below.

ΔL1=ΔYo X(1+cos θ)−ΔZo*sin θ  (1)

ΔL2=ΔYo X(1+cos θ)+ΔZo*sin θ  (2)

Accordingly, from formulas (1) and (2), ΔZo and ΔYo can be obtainedusing the following formulas (3) and (4).

ΔZo−(ΔL2−ΔL1)/2 sin θ  (3)

ΔYo=(ΔL1+ΔL2)/{2(1+cos θ)}  (4)

Therefore, displacement which is obtained using Z interferometer 43A isto be ΔZoR and ΔYoR, and displacement which is obtained using Zinterferometer 43B is to be ΔZoL and ΔYoL. And the distance betweenmeasurement beams B1 and B2 projected by Z interferometers 43A and 43B,respectively, in the X-axis direction is to be a distance D (refer toFIG. 2). Under such premises, displacement (yawing amount) Δθz ofmovable mirror 41 (more specifically wafer stage WST) in the θzdirection and displacement (rolling amount) Δθy of movable mirror 41(more specifically wafer stage WST) in the θy direction can be obtainedby the following formulas (5) and (6).

Δθz≈(ΔYoR−ΔYoL)/D  (5)

Δθy≈(ΔZoL−ΔZoR)/D  (6)

Accordingly, by using the formulas (3) to (6) above, main controller 20can compute displacement of wafer stage WST in four degrees of freedom,ΔZo, ΔYo, Δθz, and Δθy, based on the measurement results of Zinterferometers 43A and 43B.

In the manner described above, from the measurement results ofinterferometer system 118, main controller 20 can obtain displacement ofwafer stage WST in directions of six degrees of freedom (Z, X, Y, θz,θx, and θy directions). Incidentally, in the embodiment, interferometersystem 118 could measure the positional information of wafer stage WSTin directions of six degrees of freedom, however, the measurementdirection is not limited to directions of six degrees of freedom, andthe measurement direction can be directions of five degrees of freedomor less.

Incidentally, in the embodiment, the case has been described where waferstage WST (91, WTB) is a single stage that can move in six degrees offreedom, however, the present invention is not limited to this, andwafer stage WST can be configured including stage main section 91 whichcan move freely in the XY plane, and wafer table WTB mounted on stagemain section 91 that can be finely driven relative to stage main section91 at least in the Z-axis direction, the θx direction, and the θydirection. In this case, movable mirror 41 described earlier is arrangedin wafer table WTB. Further, instead of reflection surface 17 a andreflection surface 17 b, a movable mirror consisting of a plane mirrorcan be arranged in wafer table WTB.

However, in the embodiment, positional information (positionalinformation in directions of three degrees of freedom including rotaryinformation in the θz direction) of wafer stage WST (wafer table WTB) inthe XY plane is mainly measured by an encoder system described later on,and the measurement values of interferometer 16, 126, and 127 are usedsecondarily as backup or the like, such as in the case of correcting(calibrating) a long-term change (due to, for example, temporaldeformation of a scale) of the measurement values of the encoder system,and in the case of output abnormality in the encoder. Incidentally, inthe embodiment, of the positional information of wafer stage WST indirections of six degrees of freedom, positional information indirections of three degrees of freedom including the X-axis direction,the Y-axis direction and the θz direction is measured by the encodersystem described later on, and the remaining directions of three degreesof freedom, or more specifically, the positional information in theZ-axis direction, the θx direction, and the θy direction is measured bya measurement system which will also be described later that has aplurality of Z sensors. Positional information of the remainingdirections of three degrees of freedom can be measured by both themeasurement system and interferometer system 118. For example,positional information in the Z-axis direction and the θy direction canbe measured by the measurement system, and positional information in theθx direction can be measured by interferometer system 118.

Incidentally, at least part of interferometer system 118 (such as anoptical system) may be arranged at the main frame that holds projectionunit PU, or may also be arranged integrally with projection unit PU thatis supported in a suspended state as is described above, however, in theembodiment, interferometer system 118 is to be arranged at themeasurement frame described above.

Measurement stage MST includes stage main section 92 previouslydescribed, and measurement table MTB mounted on stage main section 92.Measurement table MTB is mounted on stage main section 92, via the Zleveling mechanism (not shown). However, the present invention is notlimited to this, and for example, measurement stage MST can employ theso-called coarse and fine movement structure in which measurement tableMTB can be finely driven in the X-axis direction, the Y-axis direction,and the θz direction with respect to stage main section 92, ormeasurement table MTB can be fixed to stage main section 92, and all ofmeasurement stage MST including measurement table MTB and stage mainsection 92 can be configured drivable in directions of six degrees offreedom.

Various measurement members are arranged at measurement table MTB (andstage main section 92). As such measurement members, for example, asshown in FIGS. 2 and 5A, members such as an irregular illuminance sensor94 that has a pinhole-shaped light-receiving section which receivesillumination light IL on an image plane of projection optical system PL,an aerial image measuring instrument 96 that measures an aerial image(projected image) of a pattern projected by projection optical systemPL, a wavefront aberration measuring instrument 98 by the Shack-Hartmanmethod that is disclosed in, for example, the pamphlet of InternationalPublication No. WO 03/065428 and the like are employed. As wavefrontaberration measuring instrument 98, the one disclosed in, for example,the pamphlet of International Publication No. WO 99/60361 (thecorresponding EP Patent Application Publication No. 1 079 223description) can also be used.

As irregular illuminance sensor 94, the configuration similar to the onethat is disclosed in, for example, Kokai (Japanese Unexamined PatentApplication Publication) No. 57-117238 bulletin (the corresponding U.S.Pat. No. 4,465,368 description) and the like can be used. Further, asaerial image measuring instrument 96, the configuration similar to theone that is disclosed in, for example, Kokai (Japanese Unexamined PatentApplication Publication bulletin) No. 2002-014005 (the correspondingU.S. Patent Application Publication No. 2002/0041377 description) andthe like can be used. Incidentally, three measurement members (94, 96and 98) are to be arranged at measurement stage MST in the embodiment,however, the types and/or the number of measurement members are/is notlimited to them. As the measurement members, for example, measurementmembers such as a transmittance measuring instrument that measures atransmittance of projection optical system PL, and/or a measuringinstrument that observes local liquid immersion unit 8, for example,nozzle unit 32 (or tip lens 191) or the like may also be used.Furthermore, members different from the measurement members such as acleaning member that cleans nozzle unit 32, tip lens 191 or the like mayalso be mounted on measurement stage MST.

In the embodiment, as can be seen from FIG. 5A, the sensors that arefrequently used such as irregular illuminance sensor 94 and aerial imagemeasuring instrument 96 are placed on a centerline CL (Y-axis passingthrough the center) of measurement stage MST. Therefore, in theembodiment, measurement using theses sensors can be performed by movingmeasurement stage MST only in the Y-axis direction without moving themeasurement stage in the X-axis direction.

In addition to each of the sensors described above, an illuminancemonitor that has a light-receiving section having a predetermined areasize that receives illumination light IL on the image plane ofprojection optical system PL may also be employed, which is disclosedin, for example, Kokai (Japanese Unexamined Patent ApplicationPublication bulletin) No. 11-016816 (the corresponding U.S. PatentApplication Publication No. 2002/0061469 description) and the like. Theilluminance monitor is also preferably placed on the centerline.

Incidentally, in the embodiment, liquid immersion exposure is performedin which wafer W is exposed with exposure light (illumination light) ILvia projection optical system PL and liquid (water) Lq, and accordinglyirregular illuminance sensor 94 (and the illuminance monitor), aerialimage measuring instrument 96 and wavefront aberration measuringinstrument 98 that are used in measurement using illumination light ILreceive illumination light IL via projection optical system PL and waterLq. Further, only part of each sensor such as the optical system may bemounted on measurement table MTB (and stage main section 92), or theentire sensor may be placed on measurement table MTB (and stage mainsection 92).

As shown in FIG. 5B, a frame-shaped attachment member 42 is fixed to theend surface on the −Y side of stage main section 92 of measurement stageMST. Further, to the end surface on the −Y side of stage main section92, a pair of photodetection systems 44 are fixed in the vicinity of thecenter position in the X-axis direction inside an opening of attachmentmember 42, in the placement capable of facing a pair oflight-transmitting systems 36 described previously. Each ofphotodetection systems 44 is composed of an optical system such as arelay lens, a light receiving element such as a photomultiplier tube,and a housing that houses them. As is obvious from FIGS. 4B and 5B andthe description so far, in the embodiment, in a state where wafer stageWST and measurement stage MST are closer together within a predetermineddistance in the Y-axis direction (including a contact state),illumination light IL that has been transmitted through each aerialimage measurement slit pattern SL of measurement plate 30 is guided byeach light-transmitting system 36 and received by each light receivingelement of each photodetection system 44. That is, measurement plate 30,light-transmitting systems 36 and photodetection systems 44 constitutean aerial image measuring unit 45 (refer to FIG. 6), which is similar tothe one disclosed in Kokai (Japanese Unexamined Patent ApplicationPublication) No. 2002-014005 bulletin (the corresponding U.S. PatentApplication Publication No. 2002/0041377 description) referred topreviously, and the like.

On attachment member 42, a confidential bar (hereinafter, shortlyreferred to as a “CD bar”) 46 that is made up of a bar-shaped memberhaving a rectangular sectional shape and serves as a reference member isarranged extending in the X-axis direction. CD bar 46 is kinematicallysupported on measurement stage MST by a full-kinematic mount structure.

Since CD bar 46 serves as a prototype standard (measurement standard),an optical glass ceramic that has a low thermal expansion, such asZerodur (the brand name) of Schott AG is employed as the material. Theflatness degree of the upper surface (the surface) of CD bar 46 is sethigh to be around the same level as a so-called datum plane plate.Further, as shown in FIG. 5A, a reference grating (e.g. diffractiongrating) 52 whose periodic direction is the Y-axis direction isrespectively formed in the vicinity of the end portions on one side andthe other side in the longitudinal direction of CD bar 46. The pair ofreference gratings 52 are formed placed apart from each other at apredetermined distance (which is to be “L”) in the symmetrical placementwith respect to the center in the X-axis direction of CD bar 46, thatis, centerline CL described above.

Further, on the upper surface of CD bar 46, a plurality of referencemarks M are formed in the placement as shown in FIG. 5A. The pluralityof reference marks M are formed in three-row arrays in the Y-axisdirection in the same pitch, and the array of each row is formed beingshifted from each other by a predetermined distance in the X-axisdirection. As each of reference marks M, a two-dimensional mark having asize that can be detected by a primary alignment system and secondaryalignment systems (to be described later) is used. Reference mark M mayalso be different in shape (constitution) from fiducial mark FM, but inthe embodiment, reference mark M and fiducial mark FM have the sameconstitution and also they have the same constitution with that of analignment mark of wafer W. Incidentally, in the embodiment, the surfaceof CD bar 46 and the surface of measurement table MTB (which may includethe measurement members described above) are also covered with a liquidrepellent film (water repellent film) severally.

Also on the +Y end surface and the −X end surface of measurement tableMTB, reflection surfaces 19 a and 19 b are formed similar to wafer tableWTB as is described above (refer to FIGS. 2 and 5A). By projecting aninterferometer beam (measurement beam), as shown in FIG. 2, onreflection surfaces 19 a and 19 b and receiving a reflected light ofeach interferometer beam, a Y interferometer 18 and an X interferometer130 (X-axis interferometer 130 is not shown in FIG. 1, refer to FIG. 2)of interferometer system 118 (refer to FIG. 6) measure a displacement ofeach reflection surface from a datum position, that is, positionalinformation of measurement stage MST (e.g. including at least positionalinformation in the X-axis and Y-axis directions and rotation informationin the θz direction), and the measurement values are supplied to maincontroller 20.

In exposure apparatus 100 of the embodiment, in actual, a primaryalignment system AL1 is placed on straight line LV passing through thecenter of projection unit PU (optical axis AX of projection opticalsystem PL, which also coincides with the center of exposure area IA inthe embodiment) and being parallel to the Y-axis, and has a detectioncenter at a position that is spaced apart from the optical axis at apredetermined distance on the −Y side as shown in FIG. 3, althoughomitted in FIG. 1 from the viewpoint of avoiding intricacy of thedrawing. Primary alignment system AL1 is fixed to the lower surface of amain frame (not shown) via a support member 54. On one side and theother side in the X-axis direction with primary alignment system AL1 inbetween, secondary alignment systems AL2₁ and AL2₂, and AL2₃ and AL2₄whose detection centers are substantially symmetrically placed withrespect to straight line LV are severally arranged. That is, fivealignment systems AL1 and AL2₁ to AL2₄ are placed so that theirdetection centers are placed at different positions in the X-axisdirection, that is, placed along the X-axis direction.

As is representatively shown by secondary alignment system AL2₄, eachsecondary alignment system AL2_(1I) (n=1 to 4) is fixed to a tip(turning end) of an arm 56 _(n) (n=1 to 4) that can turn around arotation center O as the center in a predetermined angle range inclockwise and anticlockwise directions in FIG. 3. In the embodiment, apart of each secondary alignment system AL2_(n) (e.g. including at leastan optical system that irradiates an alignment light to a detection areaand also leads the light that is generated from a subject mark withinthe detection area to a light-receiving element) is fixed to arm 56 _(n)and the remaining section is arranged at the main frame that holdsprojection unit PU. The X-positions of secondary alignment systems AL2₁,AL2₂, AL2₃ and AL2₄ are severally adjusted by rotating around rotationcenter O as the center. In other words, the detection areas (or thedetection centers) of secondary alignment systems AL2₁, AL2₂, AL2₃ andAL2₄ are independently movable in the X-axis direction. Accordingly, therelative positions of the detection areas of primary alignment systemAL1 and secondary alignment systems AL2₁, AL2₂, AL2₃ and AL2₄ areadjustable in the X-axis direction. Incidentally, in the embodiment, theX-positions of secondary alignment systems AL2₁, AL2₂, AL2₃ and AL2₄ areto be adjusted by the rotation of the arms. However, the presentinvention is not limited to this, and a drive mechanism that drivessecondary alignment systems AL2₁, AL2₂, AL2₃ and AL2₄ back and forth inthe X-axis direction may also be arranged. Further, at least one ofsecondary alignment systems AL2₁, AL2₂, AL2₃ and AL2₄ can be moved notonly in the X-axis direction but also in the Y-axis direction.Incidentally, since part of each secondary alignment system AL2_(n) ismoved by arm 56 _(n), positional information of the part that is fixedto arm 56 _(n) is measurable by a sensor (not shown) such as, forexample, an interferometer or an encoder. The sensor may only measureposition information in the X-axis direction of secondary alignmentsystem AL2_(n), or may be capable of measuring position information inanother direction, for example, the Y-axis direction and/or the rotationdirection (including at least one of the θx and θy directions).

On the upper surface of each arm 56 _(n), a vacuum pad 58 _(n) (n=1 to4) that is composed of a differential evacuation type air bearing isarranged. Further, aim 56 _(n) is rotated by a rotation drive mechanism60 _(n) (n=1 to 4, not shown in FIG. 3, refer to FIG. 6) that includes amotor or the like, in response to instructions of main controller 20.Main controller 20 activates each vacuum pad 58 _(n) to fix each arm 56_(n) to a main frame (not shown) by suction after rotation adjustment ofarm 56 _(n). Thus, the state of each arm 56 _(n) after rotation angleadjustment, that is, a desired positional relation of four secondaryalignment systems AL2₁ to AL2₄ with respect to primary alignment systemAL1 is maintained.

Incidentally, in the case a portion of the main frame facing arm 56 _(n)is a magnetic body, an electromagnet may also be employed instead ofvacuum pad 58.

In the embodiment, as each of primary alignment system AU and foursecondary alignment systems AL2₁ to AL2₄, for example, a sensor of anFIA (Field Image Alignment) system by an image processing method is usedthat irradiates a broadband detection beam that does not expose resiston a wafer to a subject mark, and picks up an image of the subject markformed on a light-receiving plane by the reflected light from thesubject mark and an image of an index (an index pattern on an indexplate arranged within each alignment system) (not shown), using animaging device (such as CCD), and then outputs their imaging signals.The imaging signal from each of primary alignment system AL1 and foursecondary alignment systems AL2₁ to AL2₄ is supplied to main controller20 in FIG. 6.

Incidentally, each of the alignment systems described above is notlimited to the FIA system, and an alignment sensor, which irradiates acoherent detection light to a subject mark and detects a scattered lightor a diffracted light generated from the subject mark or makes twodiffracted lights (e.g. diffracted lights of the same order ordiffracted lights being diffracted in the same direction) generated fromthe subject mark interfere and detects an interference light, cannaturally be used alone or in combination as needed. Further, fivealignment systems AL1 and AL2₁ to AL2₄ are to be arranged in theembodiment. However, the number of alignment systems is not limited tofive, but may be the number equal to or more than two and equal to orless than four, or may be the number equal to or more than six, or maybe the even number, not the odd number. Moreover, in the embodiment,five alignment systems AU and AL2₁ to AL2₄ are to be fixed to the lowersurface of the main frame that holds projection unit PU, via supportmember 54. However, the present invention is not limited to this, andfor example, the five alignment systems may also be arranged on themeasurement frame described earlier. Further, because alignment systemsAL1 and AL2₁ to AL2₄ detect alignment marks on wafer W and referencemarks on and CD bar 46, in the embodiment, the systems will also besimply referred to as a mark detection system.

In exposure apparatus 100 of the embodiment, as shown in FIG. 3, fourhead units 62A to 62D of the encoder system are placed in a state ofsurrounding nozzle unit 32 on all four sides. In actual, head units 62Ato 62D are fixed to the foregoing main frame that holds projection unitPU in a suspended state via a support member, although omitted in FIG. 3from the viewpoint of avoiding intricacy of the drawings. Incidentally,for example, in the case projection unit PU is supported in a suspendedstate, head units 62A to 62D may be supported in a suspended stateintegrally with projection unit PU, or may be arranged at themeasurement frame described above.

Head units 62A and 62C are respectively placed on the +X side and −Xside of projection unit PU having the longitudinal direction in theX-axis direction, and are also placed apart at the substantially samedistance from optical axis AX of projection optical system PLsymmetrically with respect to optical axis AX of projection opticalsystem PL. Further, head units 62B and 62D are respectively placed onthe +Y side and −Y side of projection unit PU having the longitudinaldirection in the Y-axis direction and are also placed apart at thesubstantially same distance from optical axis AX of projection opticalsystem PL.

As shown in FIG. 3, head units 62A and 62C are each equipped with aplurality of (six in this case) Y heads 64 that are placed at apredetermined distance on a straight line LH that passes through opticalaxis AX of projection optical system PL and is parallel to the X-axis,along the X-axis direction. Head unit 62A constitutes a multiple-lens(six-lens in this case) Y linear encoder (hereinafter, shortly referredto as a “Y encoder” or an “encoder” as needed) 70A (refer to FIG. 6)that measures the position in the Y-axis direction (the Y-position) ofwafer stage WST (wafer table WTB) using Y scale 39Y₁ described above.Similarly, head unit 62C constitutes a multiple-lens (six-lens, in thiscase) Y linear encoder 70C (refer to FIG. 6) that measures theY-position of wafer stage WST (wafer table WTB) using Y scale 39Y₂described above. In this case, a distance between adjacent Y heads 64(i.e. measurement beams) equipped in head units 62A and 62C is setshorter than a width in the X-axis direction of Y scales 39Y₁ and 39Y₂(to be more accurate, a length of grid line 38). Further, out of aplurality of Y heads 64 that are equipped in each of head units 62A and62C, Y head 64 located innermost is fixed to the lower end portion ofbarrel 40 of projection optical system PL (to be more accurate, to theside of nozzle unit 32 enclosing tip lens 191) so as to be placed asclose as possible to the optical axis of projection optical system PL.

As shown in FIG. 3, head unit 62B is equipped with a plurality of (sevenin this case) X heads 66 that are placed on straight line LV at apredetermined distance along the Y-axis direction. Further, head unit62D is equipped with a plurality of (eleven in this case, out of elevenX heads, however, three X heads that overlap primary alignment systemAL1 are not shown in FIG. 3) X heads 66 that are placed on straight lineLV at a predetermined distance. Head unit 62B constitutes amultiple-lens (seven-lens, in this case) X linear encoder (hereinafter,shortly referred to as an “X encoder” or an “encoder” as needed) 70B(refer to FIG. 6) that measures the position in the X-axis direction(the X-position) of wafer stage WST (wafer table WTB) using X scale 39X₁described above. Further, head unit 62D constitutes a multiple-lens(eleven-lens, in this case) X linear encoder 70D (refer to FIG. 6) thatmeasures the X-position of wafer stage WST (wafer table WTB) using Xscale 39X₂ described above. Further, in the embodiment, for example, atthe time of alignment (to be described later) or the like, two X heads66 out of eleven X heads 66 that are equipped in head unit 62Dsimultaneously face X scale 39X₁ and X scale 39X₂ respectively in somecases. In these cases, X scale 39X₁ and X head 66 facing X scale 39X₁constitute X linear encoder 70B, and X scale 39X₂ and X head 66 facing Xscale 39X₂ constitute X linear encoder 70D. Herein, some of eleven Xheads 66, in this case, three X heads are attached to the lower surfaceside of support member 54 of primary alignment system AL1.

Further, a distance between adjacent X heads 66 (measurement beams) thatare equipped in each of head units 62B and 62D is set shorter than awidth in the Y-axis direction of X scales 39X₁ and 39X₂ (to be moreaccurate, a length of grid line 37). Further, X head 66 locatedinnermost out of a plurality of X heads 66 that are quipped in each ofhead units 62B and 62D is fixed to the lower end portion of the barrelof projection optical system PL (to be more accurate, to the side ofnozzle unit 32 enclosing tip lens 191) so as to be placed as close aspossible to the optical axis of projection optical system PL.

Moreover, on the −X side of secondary alignment system AL2₁ and on the+X side of secondary alignment system AL2₄, Y heads 64 y ₁ and 64 y ₂are respectively arranged, whose detection points are placed on astraight line parallel to the X-axis that passes through the detectioncenter of primary alignment system AL1 and are substantiallysymmetrically placed with respect to the detection center. The distancebetween Y heads 64 y ₁ and 64 y ₂ is set substantially equal to distanceL described previously. Y heads 64 y ₁ and 64 y ₂ face Y scales 39Y₂ and39Y₁ respectively in a state where the center of wafer W on wafer stageWST is on straight line LV as shown in FIG. 3. On an alignment operation(to be described later) or the like, Y scales 39Y₂ and 39Y₁ are placedfacing Y heads 64 y ₁ and 64 y ₂ respectively, and the Y-position (andthe θz rotation) of wafer stage WST is measured by Y heads 64 y ₁ and 64y ₂ (i.e. Y encoders 70C and 70A composed of Y heads 64 y ₁ and 64 y ₂).

Further, in the embodiment, at the time of baseline measurement of thesecondary alignment systems (to be described later) or the like, a pairof reference gratings 52 of CD bar 46 face Y heads 64 y ₁ and 64 y ₂respectively, and the Y-position of CD bar 46 is measured at theposition of each of reference gratings 52 by Y heads 64 y ₁ and 64 y ₂and facing reference gratings 52. In the following description, encodersthat are composed of Y heads 64 y ₁ and 64 y ₂ facing reference gratings52 respectively are referred to as Y-axis linear encoders 70E and 70F(refer to FIG. 6).

Six linear encoders 70A to 70F described above measure the positionalinformation of wafer stage WST in each measurement direction at aresolution of, for example, around 0.1 nm, and the measurement values(measurement information) are supplied to main controller 20. Maincontroller 20 controls the position within the XY plane of wafer tableWTB based on the measurement values of linear encoders 70A to 70D, andalso controls the rotation in the θz direction of CD bar 46 based on themeasurement values of linear encoders 70E and 70F. Incidentally, theconfiguration and the like of the linear encoder will be describedfurther later in the description.

In exposure apparatus 100 of the embodiment, a position measuring unitthat measures positional information of wafer W in the Z-axis directionis arranged. As shown in FIG. 3, in the embodiment, as the positionmeasuring unit, a multipoint focal position detecting system(hereinafter, shortly referred to as a “multipoint AF system”) by anoblique incident method is arranged, which is composed of an irradiationsystem 90 a and a photodetection system 90 b, and has the configurationsimilar to the one disclosed in, for example, Kokai (Japanese UnexaminedPatent Application Publication) No. 06-283403 bulletin (thecorresponding U.S. Pat. No. 5,448,332 description) and the like. In theembodiment, as an example, irradiation system 90 a is placed on the −Yside of the −X end portion of head unit 62C and photodetection system 90b is placed on the −Y side of the +X end portion of head unit 62A in astate of opposing irradiation system 90 a.

A plurality of detection points of the multipoint AF system (90 a, 90 b)are placed at a predetermined distance along the X-axis direction on thesurface to be detected, although it is omitted in the drawings. In theembodiment, the plurality of detection points are placed, for example,in the arrangement of a matrix having one row and M columns (M is atotal number of detection points) or having two rows and N columns (N isa half of a total number of detection points). In FIG. 3, the pluralityof detection points to which a detection beam is severally irradiatedare not individually shown, but are shown as an elongate detection area(beam area) AF that extends in the X-axis direction between irradiationsystem 90 a and photodetection system 90 b. Since the length ofdetection area AF in the X-axis direction is set to around the same asthe diameter of wafer W, position information (surface positioninformation) in the Z-axis direction across the entire surface of waferW can be measured by only scanning wafer W in the Y-axis direction once.Further, since detection area AF is placed between liquid immersion area14 (exposure area IA) and the detection areas of the alignment systems(AL1, AL2₁, AL2₂, AL2₃ and AL2₄) in the Y-axis direction, the detectionoperations of the multipoint AF system and the alignment systems can beperformed in parallel. The multipoint AF system may also be arranged onthe main frame that holds projection unit PU or the like, but is to bearranged on the measurement frame described earlier in the embodiment.

Incidentally, the plurality of detection points are to be placed in onerow and M columns, or two rows and N columns, but the number(s) of rowsand/or columns is/are not limited to these numbers. However, in the casethe number of rows is two or more, the positions in the X-axis directionof detection points are preferably made to be different even between thedifferent rows. Moreover, the plurality of detection points is to beplaced along the X-axis direction. However, the present invention is notlimited to this, and all of or some of the plurality of detection pointsmay also be placed at different positions in the Y-axis direction. Forexample, the plurality of detection points may also be placed along adirection that intersects both of the X-axis and the Y-axis. That is,the positions of the plurality of detection points only have to bedifferent at least in the X-axis direction. Further, a detection beam isto be irradiated to the plurality of detection points in the embodiment,but a detection beam may also be irradiated to, for example, the entirearea of detection area AF. Furthermore, the length of detection area AFin the X-axis direction does not have to be nearly the same as thediameter of wafer W.

In the embodiment, in the vicinity of detection points located at bothends out of a plurality of detection points of the multipoint AF system,that is, in the vicinity of both end portions of beam area AF, one eachpair of surface position sensors for Z position measurement(hereinafter, shortly referred to as “Z sensors”), that is, a pair of Zsensors 72 a and 72 b and a pair of Z sensors 72 c and 72 d are arrangedin the symmetrical placement with respect to straight line LV. Z sensors72 a to 72 d are fixed to the lower surface of a main frame (not shown).As Z sensors 72 a to 72 d, a sensor that irradiates a light to wafertable WTB from above, receives the reflected light and measures positioninformation of the wafer table WTB surface in the Z-axis directionorthogonal to the XY plane, as an example, an optical displacementsensor (sensor by an optical pickup method), which has the configurationlike an optical pickup used in a CD drive unit, is used. Incidentally, Zsensors 72 a to 72 d may also be arranged on the measurement framedescribed above or the like. Moreover, head unit 62C is equipped with aplurality of (in this case six each, which is a total of twelve) Zsensors 74 _(i,j) (i=1, 2, j=1, 2, 6), which are placed corresponding toeach other along two straight lines at a predetermined distance, thestraight lines being parallel to straight line LH and are located on oneside and the other side of straight line LH in the X-axis direction thatconnects a plurality of Y heads 64. In this case, Z sensors 74 _(1,j)and 74 _(2,j) that make a pair are disposed symmetrical to straight lineLH. Furthermore, the plurality of pairs (in this case, six pairs) of Zsensors 74 _(1,j) and 74 _(2,j) and a plurality of Y heads 64 are placedalternately in the X-axis direction. As each Z sensor 74 _(i,j), asensor by an optical pickup method similar to Z sensors 72 a to 72 d isused.

In this case, the distance between each pair of Z sensors 74 _(1,j) and74 _(2,j) that are located symmetrically with respect to straight lineLH is set to be the same distance as the distance between Z sensors 74 aand 74 b previously described. Further, a pair of Z sensors 74 _(1,4)and 74 _(2,4) are located on the same straight line in the Y-axisdirection as Z sensors 72 a and 72 b.

Further, head unit 62A is equipped with a plurality of (twelve in thiscase) Z sensors 76 _(p,q) (p=1, 2 and q=1, 2, 6) that are placedsymmetrically to a plurality of Z sensors 74 _(i,j) with respect tostraight line LV. As each Z sensor 74 _(p,q), a sensor by an opticalpickup method similar to Z sensors 72 a to 72 d is used. Further, a pairof Z sensors 76 _(1,3) and 76 _(2,3) are located on the same straightline in the Y-axis direction as Z sensors 72 c and 72 d. Incidentally, Zsensors 74 _(i,j) and 76 _(p,q) are installed, for example, at themainframe or the measurement frame previously described. Further, in theembodiment, the measurement system that has Z sensors 72 a to 72 d, and74 _(i,j) and 76 _(p,q) measures positional information of wafer stageWST in the Z-axis direction using one or a plurality of Z sensors thatface the scale previously described. Therefore, in the exposureoperation, Z sensors 74 _(i,j) and 76 _(p,q) used for positionmeasurement are switched, according to the movement of wafer stage WST.Furthermore, in the exposure operation, Y scale 39Y₁ and at least one Zsensor 76 _(p,q) face each other, and Y scale 39Y₂ and at least one Zsensor 74 _(i,j) also face each other. Accordingly, the measurementsystem can measure not only positional information of wafer stage WST inthe Z-axis direction, but also positional information (rolling) in theθy direction. Further, in the embodiment, each Z sensor of themeasurement system detects a grating surface (a formation surface of adiffraction grating) of the scale, however, the measurement system canalso detect a surface that is different from the grating surface, suchas, for example, a surface of the cover glass that covers the gratingsurface.

Incidentally, in FIG. 3, measurement stage MST is omitted and a liquidimmersion area that is formed by water Lq held in the space betweenmeasurement stage MST and tip lens 191 is shown by a reference code 14.Further, in FIG. 3, a reference code 78 indicates a localair-conditioning system that blows dry air whose temperature is adjustedto a predetermined temperature to the vicinity of a beam path of themultipoint AF system (90 a, 90 b) by, for example, downflow as isindicated by outline arrows in FIG. 3. Further, a reference code UPindicates an unloading position where a wafer on wafer table WTB isunloaded, and a reference code LP indicates a loading position where awafer is loaded on wafer table WTB. In the embodiment, unloadingposition UP and loading position LP are set symmetrically with respectto straight line LV. Incidentally, unloading position UP and loadingposition LP may be the same position.

FIG. 6 shows the main configuration of the control system of exposureapparatus 100. The control system is mainly configured of maincontroller 20 composed of a microcomputer (or workstation) that performsoverall control of the entire apparatus. In a memory 34 which is anauxiliary memory connecting to main controller 20, correctioninformation, which will be described below, is stored. Incidentally, inFIG. 6, various sensors such as irregular illuminance sensor 94, aerialimage measuring instrument 96 and wavefront aberration measuringinstrument 98 that are arranged at measurement stage MST arecollectively shown as a sensor group 99.

In exposure apparatus 100 of the embodiment which is configured in themanner described above, because the placement of the X scales and Yscales on wafer table WTB and the arrangement of the X heads and Y headswhich were described above were employed, in the effective stroke range(more specifically, in the embodiment, the range in which the stagemoves for alignment and exposure operation) of wafer stage WST, at leastone X head 66 in the total of 18 X heads belonging to head units 62B and62D must face at least one of X scale 39X₁ and 39X₂, and at least one Yhead 64 each, or Y head 64 y ₁ and 64 y ₂ belonging to head units 62Aand 62C, also respectively face Y scales 39Y₁ and 39Y₂, respectively, asillustrated in FIGS. 7A and 7B. That is, at least one each of thecorresponding heads is made to face at least the three out of the fourscales.

Incidentally, in FIGS. 7A and 7B, the head which faces the correspondingX scale or Y scale is shown surrounded in a circle.

Therefore, in the effective stroke range of wafer stage WST referred toearlier, by controlling each motor that configures stage drive system124, based on at least a total of three measurement values of theencoders, which are encoders 70A and 70C, and at least one of encoders70B and 70D, main controller 20 can control the position (including a θzrotation) of wafer stage WST in the XY plane with high accuracy. Becausethe effect of the air fluctuation that the measurement values of encoder70A to 70D receive is small enough so that it can be ignored whencompared with an interferometer, the short-term stability of themeasurement affected by the air fluctuation is remarkably good whencompared with the interferometer.

Further, when wafer stage WST is driven in the X-axis direction as isshown by an outlined arrow in FIG. 7A, Y heads 64 that measure theposition of wafer stage WST in the Y-axis direction are sequentiallyswitched, as is indicated by arrows e₁ and e₂ in the drawing, to theadjacent Y heads 64. For example, the heads are switched from Y heads 64_(C3) and 64 _(A3) surrounded by a solid circle to Y heads 64 _(C4) and64 _(A4) that are surrounded by a dotted circle. Therefore, before orafter this switching, linkage process of the measurement values whichwill be described later on is performed. More specifically, in theembodiment, in order to perform the switching of the Y heads 64 and thelinkage process of the measurement value smoothly, the distance betweenadjacent Y heads 64 that head units 62A and 62 have is set smaller thanthe width of Y scales 39Y₁ and 39Y₂ in the X-axis direction.

Further, in the embodiment, since a distance between adjacent X heads 66that are equipped in head units 62B and 62D is set narrower than a widthof X scales 39X₁ and 39X₂ in the Y-axis direction as is describedpreviously, when wafer stage WST is driven in the Y-axis direction asindicated by an outline arrow in FIG. 7B, X head 66 that measures theposition in the X-axis direction of wafer stage WST is sequentiallyswitched to adjacent X head 66 (e.g. X head 66 circled by a solid lineis switched to X head 66 circled by a dotted line), and the measurementvalues are transferred before and after the switching.

Next, the configuration of encoders 70A to 70F will be described,focusing on Y encoder 70A that is enlargedly shown in FIG. 8A, as arepresentative. FIG. 8A shows one Y head 64 of head unit 62A thatirradiates a detection light (measurement beam) to Y scale 39Y₁.

Y head 64 is mainly composed of three sections, which are an irradiationsystem 64 a, an optical system 64 b and a photodetection system 64 c.

Irradiation system 64 a includes a light source that emits a laser beamLB in a direction inclined at an angle of 45 degrees with respect to theY-axis and Z-axis, for example, a semiconductor laser LD, and aconverging lens L1 that is placed on the optical path of laser beam LBemitted from semiconductor laser LD.

Optical system 64 b is equipped with a polarization beam splitter PBSwhose separation plane is parallel to an XZ plane, a pair of reflectionmirrors R1a and R1b, lenses L2a and L2b, quarter wavelength plates(hereinafter, referred to as a λ/4 plate) WP1a and WP1b, refectionmirrors R2a and R2b, and the like.

Photodetection system 64 c includes a polarizer (analyzer), aphotodetector, and the like.

In Y encoder 70A, laser beam LB emitted from semiconductor laser LD isincident on polarization beam splitter PBS via lens L1, and is split bypolarization into two beams LB₁ and LB₂. Beam LB₁ having beentransmitted through polarization beam splitter PBS reaches reflectivediffraction grating RG that is formed on Y scale 39Y₁, via reflectionmirror R1_(a), and beam LB₂ reflected off polarization beam splitter PBSreaches reflective diffraction grating RG via reflection mirror R1b.Incidentally, “split by polarization” in this case means the splittingof an incident beam into a P-polarization component and anS-polarization component.

Predetermined-order diffraction beams that are generated fromdiffraction grating RG due to irradiation of beams LB₁ and LB₂, forexample, the first-order diffraction beams are severally converted intoa circular polarized light by λ/4 plates WP1b and WP1a via lenses L2band L2a, and reflected by reflection mirrors R2b and R2a and then thebeams pass through λ/4 plates WP1b and WP1a again and reach polarizationbeam splitter PBS by tracing the same optical path in the reverseddirection. Each of the polarization directions of the two beams thathave reached polarization beam splitter PBS is rotated at an angle of 90degrees with respect to the original direction. Therefore, thefirst-order diffraction beam of beam LB₁ that was previously transmittedthrough polarization beam splitter PBS is reflected off polarizationbeam splitter PBS and is incident on photodetection system 64 c, andalso the first-order diffraction beam of beam LB₂ that was previouslyreflected off polarization beam splitter PBS is transmitted throughpolarization beam splitter PBS and is synthesized concentrically withthe first-order diffraction beam of beam LB₁ and is incident onphotodetection system 64 c.

Then, the polarization directions of the two first-order diffractionbeams described above are uniformly arranged by the analyzer insidephotodetection system 64 c and the beams interfere with each other to bean interference light, and the interference light is detected by thephotodetector and is converted into an electric signal in accordancewith the intensity of the interference light.

As is obvious from the above description, in Y encoder 70A, since theoptical path lengths of the two beams to be interfered are extremelyshort and also are almost equal to each other, the influence by airfluctuations can mostly be ignored. Then, when Y scale 39Y₁ (morespecifically, wafer stage WST) moves in a measurement direction (in thiscase, the Y-axis direction), the phase of the two beams changes,respectively, which changes the intensity of the interference light.This change in the intensity of the interference light is detected byphotodetection system 64 c, and positional information corresponding tothe intensity change is output as a measurement value of Y encoder 70A.Other encoders 70B, 70C, 70D, 70E, and 70F are also configured similarlywith encoder 70A.

Meanwhile, when wafer stage WST moves in a direction different from theY-axis direction and a relative motion (a relative motion in a directionbesides the measurement direction) occurs between head 64 and Y scale39Y₁ in a direction besides the direction that should be measured, inmost cases, a measurement error occurs in Y encoder 70A due to suchmotion. Hereinafter, the mechanism of this measurement error generationwill be described.

First of all, a relation between the intensity of interference lightthat is synthesized from two return beams LB₁ and LB₂ and displacement(relative displacement with Y head 64) of Y scale 39Y₂ (reflectiongrating RG) is derived.

In FIG. 8B, supposing that beam LB₁, which was reflected off reflectionmirror R1a, is incident on reflection grating RG at an angle θ_(a0), andan n_(a) ^(th) order diffraction light is to be generated at an angleθ_(a1). And the return beam, which is reflected off reflection mirrorR2a and follows the return path, is incident on reflection grating RG atan angle θ_(a1). Then, a diffraction light is generated again. In thiscase, the diffraction light that occurs at angle θ_(a0) and moves towardreflection mirror R1a following the original optical path is an n_(a)^(th) order diffraction light, which is a diffraction light of the sameorder as the diffraction light generated on the outward path.

Meanwhile, beam LB₂ reflected off reflection mirror R1b is incident onreflection grating RG at an angle θ_(b0), and an n_(b) ^(th) orderdiffraction light is generated at an angle θ_(b1). Supposing that thisdiffraction light is reflected off reflection mirror R2b and returns toreflection mirror R1b following the same optical path.

In this case, intensity I of the interference light synthesized by thetwo return beams LB₁ and LB₂ is dependent on a phase difference φbetween the two return beams LB₁ and LB₂ in the light receiving positionof the photodetector, by I∝1+cos φ. However, the intensity of the twobeams LB₁ and LB₂ was to be equal to each other.

Details on deriving phase difference φ are omitted here, however, phasedifference is theoretically obtained by formula (7) below.

φ=KΔL+4π(n _(b) −n _(a))ΔY/p+2KΔZ(cos θ_(b1)+cos θ_(b0)−cos θ_(a1)−cosθ_(a0))  (7)

In this case, KΔL is the phase difference due to an optical pathdifference ΔL of the two beams LB₁ and LB₂, ΔY is displacement ofreflection grating RG in the +Y direction, ΔZ is displacement ofreflection grating RG in the +Z direction, p is the pitch of thediffraction grating, and n_(b) and n_(a) are the diffraction order ofeach diffraction light described above.

Suppose that the encoder is configured so as to satisfy optical pathdifference ΔL=0 and a symmetry shown in the following formula (8).

θ_(a0)=θ_(b0),θ_(a1)=θ_(b1)  (8)

In such a case, inside the parenthesis of the third term on theright-hand side of formula (7) becomes zero, and also at the same timen_(b)=−n_(a)(=n), therefore, the following formula (9) can be obtained.

φ_(sym)(ΔY)=2πΔY/(p/4n)  (9)

From formula (9) above, it can be seen that phase difference is notdependent on the wavelength of the light.

As a simple example, two cases shown in FIGS. 9A and 9B will now beconsidered. First of all, in the case of FIG. 9A, an optical axis ofhead 64 coincides with the Z-axis direction (head 64 is not inclined).Supposing that wafer stage WST was displaced in the Z-axis direction(ΔZ≠0,ΔY=0). In this case, because there are no changes in optical pathdifference ΔL, there are no changes in the first teen on the right-handside of formula (7). The second term becomes zero, according to asupposition ΔY=0. And, the third term becomes zero because it satisfiesthe symmetry of formula (8). Accordingly, no change occurs in phasedifference φ, and further no intensity change of the interference lightoccurs. As a result, the measurement value (count value) of the encoderalso does not change.

Meanwhile, in the case of FIG. 9B, the optical axis of head 64 isinclined (head 64 is inclined) with respect to the Z-axis. Supposingthat wafer stage WST was displaced in the Z-axis direction from thisstate (ΔZ≠0, ΔY=0). In this case as well, because there are no changesin optical path difference ΔL, there are no changes in the first term onthe right-hand side of formula (7). And, the second term becomes zero,according to supposition ΔY=0. However, because the head is inclined thesymmetry of formula (8) will be lost, and the third term will not becomezero and will change in proportion to Z displacement ΔZ. Accordingly, achange occurs in phase difference φ, and as a consequence, themeasurement value changes. Incidentally, even if head 64 is notgradient, for example, depending on the optical properties (such astelecentricity) of the head the symmetry of formula (8) is lost, and themeasurement value changes likewise. More specifically, characteristicinformation of the head unit, which is a generation factor of themeasurement error of the encoder system, includes not only the gradientof the head but also the optical properties as well.

Further, although it is omitted in the drawings, in the casedisplacement occurs in a direction perpendicular to the measurementdirection (the Y-axis direction) and the optical axis direction (theZ-axis direction), (ΔX≠0,ΔY=0,ΔZ=0), the measurement value does notchange as long as the direction (longitudinal direction) in which thegrid line of diffraction grating RG faces is orthogonal to themeasurement direction, however, in the case the direction is notorthogonal, sensitivity occurs with a gain proportional to the angle.

Next, four cases as shown in, for example, FIGS. 10A to 10D, will beconsidered. First of all, in the case of FIG. 10A, the optical axis ofhead 64 coincides with the Z-axis direction (head 64 is not inclined).Even if wafer stage WST moves in the +Z direction and shifts to acondition shown in FIG. 10B from this state, the measurement value ofthe encoder does not change since the case is the same as in FIG. 9Apreviously described.

Next, suppose that wafer stage WST rotates around the X-axis from thestate shown in FIG. 10B and moves into a state shown in FIG. 10C. Inthis case, although the head and the scale do not perform relativemotion, or more specifically, even though ΔY=ΔZ=0, a change occurs inoptical path difference ΔL due to the rotation of wafer stage WST, whichchanges the measurement value of the encoder. That is, a measurementerror occurs in the encoder system due to an inclination (tilt) of waferstage WST. Next, suppose that wafer stage WST moves downward from astate shown in

FIG. 10C and moves into a state shown in FIG. 10D. In this case, achange in optical path difference ΔL does not occur because wafer stageWST does not rotate. However, because the symmetry of formula (8) hasbeen lost, phase difference φ changes by Z displacement ΔZ through thethird term on the right-hand side of formula (7). Accordingly, themeasurement value of the encoder changes. Incidentally, the measurementvalue of the encoder in the case of FIG. 10D becomes the samemeasurement value as the case in FIG. 10A.

According to a result of a simulation that the inventors and the likeperformed, it became clear that the measurement value of the encoder hassensitivity not only to a positional change of the scale in the Y-axisdirection, which is the measurement direction, but also has sensitivityto an attitude change in the θx direction (the pitching direction) andthe θz direction (the yawing direction), and moreover, depends on thepositional change in the Z-axis direction in the case such as when thesymmetry has been lost as is previously described. That is, thetheoretical description previously described agreed with the result ofthe simulation.

Therefore, in the embodiment, correction information to correct themeasurement error of each encoder caused by the relative motion of thehead and the scale in the direction besides the measurement direction isacquired as follows.

a. First of all, main controller 20 drives wafer stage WST via stagedrive system 124, while monitoring the measurement values of Yinterferometer 16 of interferometer system 118, X interferometer 126,and Z interferometers 43A and 43B, and as shown in FIGS. 11A and 11B,makes Y head 64 located farthest to the −X side of head unit 62A face anarbitrary area (an area circled in FIG. 11A) AR of Y scale 39Y₁ on theupper surface of wafer table WTB.

b. Then, based on the measurement values of Y interferometer 16 and Zinterferometers 43A and 43B, main controller 20 drives wafer table WTB(wafer stage WST) so that a rolling amount θy and yawing amount θz ofwafer table WTB (wafer stage WST) both become zero while a pitchingamount θx also becomes a desired value α₀ (in this case, α₀=200 μrad),irradiates a detection light on area AR of Y scale 39Y₁ from head 64above after the drive, and stores the measurement value whichcorresponds to a photoelectric conversion signal from head 64 which hasreceived the reflected light in an internal memory.

c. Next, while maintaining the attitude (pitching amount θx=α₀, yawingamount θz=0, rolling amount θy=0) of wafer table WTB (wafer stage WST)based on the measurement values of Y interferometer 16 and Zinterferometers 43A and 43B, main controller 20 drives wafer table WTB(wafer stage WST) within a predetermined range, such as, for example,the range of −100 μm to +100 μm in the Z-axis direction as is indicatedby an arrow in FIG. 11B, sequentially takes in the measurement valuescorresponding to the photoelectric conversion signals from head 64 whichhas received the reflected light at a predetermined sampling intervalwhile irradiating a detection light on area AR of Y scale 39Y₁ from head64 during the drive, and stores the values in the internal memory.

d. Next, main controller 20 changes pitching amount θx of wafer tableWTB (wafer stage WST) to (α=α₀−Δα), based on the measurement values of Yinterferometer 16.

e. Then, as for the attitude after the change, main controller 20repeats an operation similar to c. described above.

f. Then, main controller 20 alternately repeats the operations of d. ande described above, and for a range where pitching amount θx is, forexample, −200 μrad<θx<+200 μrad, takes in the measurement values of head64 within the Z drive range described above atΔα(rad), at an intervalof, for example, 40 μrad.

g. Next, by plotting each data within the internal memory obtained bythe processes b. to e. described above on a two-dimensional coordinatesystem whose horizontal axis indicates a Z position and vertical axisindicates an encoder count value, sequentially linking plot points wherethe pitching amounts are the same, and shifting the horizontal axis inthe vertical axis direction so that a line (a horizontal line in thecenter) which indicates a zero pitching amount passes through theorigin, main controller 20 can obtain a graph (a graph that shows achange characteristic of the measurement values of the encoder (head)according to the Z leveling of the wafer stage) like the one shown inFIG. 12.

The values of the vertical axis at each point on the graph in FIG. 12 isnone other than the measurement error of the encoder in each Z position,in pitching amount θx=a. Therefore, main controller 20 sees pitchingamount θx, the Z position, and the encoder measurement error at eachpoint on the graph in FIG. 12 as a table data, and stores the table datain memory 34 (refer to FIG. 6) as stage position induced errorcorrection information. Or main controller 20 sees the measurement erroras a function of Z position z and pitching amount θx, and obtains thefunction computing an undetermined coefficient, for example, by theleast-squares method, and stores the function in memory 34 as stageposition induced error correction information.

h. Next, main controller 20 drives wafer stage WST in the −X-directionby a predetermined amount via stage drive system 124 while monitoringthe measurement values of X interferometer 126 of interferometer system118, and as shown in FIG. 13, makes Y head 64 located second from theedge on the −X side of head unit 62A (the Y head next to Y head 64 whosedata has already been acquired in the process described above) face areaAR previously described (the area circled in FIG. 13) of Y scale 39Y₁ onthe upper surface of wafer table WTB.

i. Then, main controller 20 performs a process similar to the onesdescribed above on Y head 64, and stores correction information of Yencoder 70A configured by head 64 and Y scale 39Y₁ in memory 34.

j. Hereinafter, in a similar manner, main controller 20 respectivelyobtains correction information of Y encoder 70A configured by eachremaining Y head 64 of head unit 62A and Y scale 39Y₁, correctioninformation of X encoder 70B configured by each X head 66 of head unit62B and X scale 39X₁, correction information of Y encoder 70C configuredby each X head 64 of head unit 62C and Y scale 39Y₂, and correctioninformation of X encoder 70D configured by each X head 66 of head unit62D and X scale 39X₂, and stores them in memory 34.

In this case, it is important that the same area on X scale 39X₁ is usedon the measurement using each X head 66 of head unit 62B describedabove, the same area on Y scale 39Y₂ is used on the measurement usingeach Y head 64 of head unit 62C, and the same area in X scale 39X₂ isused on the measurement using each Y head 66 of head unit 62D. Thereason for this is because if the correction (including the curvecorrection of reflection surfaces 17 a and 17 b, and reflection surfaces41 a, 41 b, and 41 c) of each interferometer of interferometer system118 has been completed, the attitude of wafer stage WST can be set to adesired attitude anytime based on the measurement values of theinterferometers, and by using the same location of each scale, even ifthe scale surface is inclined, the measurement error caused by theeffect of the inclination does not occur between the heads.

Further, main controller 20 performs the measurement described above forY heads 64 y ₁ and 64 y ₂ using the same area on Y scale 39Y₁ and 39Y₂,respectively, which is the same as each Y head 64 of head units 62C and64A described above, obtains correction information of encoder 70Cconfigured by Y head 64 y ₁ which faces Y scale 39Y₂ and correctioninformation of encoder 70A configured by Y head 64 y ₂ which faces Yscale 39Y₁, and stores the information in memory 34.

Next, in a similar procedure as in the case described above where thepitching amount was changed, main controller 20 sequentially changesyawing amount θz of wafer stage WST for a range of −200 μrad<θx<+200μrad and drives wafer table WTB (wafer stage WST) in the Z-axisdirection at each position within a predetermined range, such as, forexample, within −100 μm˜+100 μm, while maintaining both the pitchingamount and the rolling amount of wafer stage WST at zero, and during thedrive, sequentially takes in the measurement values of the head at apredetermined sampling interval and stores them in the internal memory.Such a measurement is performed for all heads 64 or 66, and in aprocedure similar to the one described earlier, by plotting each datawithin the internal memory on the two-dimensional coordinate systemwhose horizontal axis indicates the Z position and vertical axisindicates the encoder count value, sequentially linking plot pointswhere the yawing amounts are the same, and shifting the horizontal axisso that a line (a horizontal line in the center) which indicates a zeropitching amount passes through the origin, main controller 20 can obtaina graph similar to the one shown in FIG. 12. Then, main controller 20regards yawing amount θz, Z position, and the measurement error at eachpoint on the obtained graph as a table data, and then stores the data inmemory 34 as correction information. Or, main controller 20 sees themeasurement error as a function of Z position z and yawing amount θz,and obtains the function computing an undetermined coefficient, forexample, by the least-squares method, and stores the function in memory34 as correction information.

In this case, the measurement error of each encoder in the case both thepitching amount and the yawing amount of wafer stage WST are not zerowhen wafer stage WST is at Z position z can safely be considered to be asimple sum of the measurement error that corresponds to the pitchingamount described above and the measurement error that corresponds to theyawing amount (a linear sum) when wafer stage WST is at Z position z.The reason for this is, as a result of simulation, it has been confirmedthat the measurement error (count value) linearly changes according tothe change of the Z position, even when the yawing is changed.

Hereinafter, to simplify the description, a function of pitching amountθx, yawing amount θz, and Z position z of wafer stage WST that expressesa measurement error Δy as shown in the next formula (10) is to beobtained for the Y heads of each Y encoder, and to be stored in memory34. Further, a function of rolling amount θy, yawing amount θz, and Zposition z of wafer stage WST that expresses a measurement error Ax asshown in the next formula (11) is to be obtained for the X heads of eachX encoder, and to be stored in memory 34.

Δy=f(z,θx,θz)=θx(z−a)+θz(z−b)  (10)

Δx=g(z,θy,θz)=θy(z−c)+θz(z−d)  (11)

In formula (10) above, a is a Z-coordinate of a point where eachstraight line intersects on the graph in FIG. 12, and b is aZ-coordinate of a point where each straight line intersects on a graphsimilar to FIG. 12 in the case when the yawing amount is changed so asto acquire the correction information of the Y encoder. Further, informula (11) above, c is a Z-coordinate of a point where each straightline intersects on a graph similar to FIG. 12 in the case when therolling amount is changed so as to acquire the correction information ofthe X encoder, and d is a Z-coordinate of a point where each straightline intersects on a graph similar to FIG. 12 in the case when theyawing amount is changed so as to acquire the correction info nation ofthe X encoder.

Incidentally, because Δy and Ax described above show the degree ofinfluence of the position of wafer stage WST in the direction besidesthe measurement direction (e. g. the θx direction or the θy direction,the θz direction and the Z-axis direction) on the measurement values ofthe Y encoder or the X encoder, in the present specification, it will bereferred to as a stage position induced error, and because the stageposition induced error can be used as it is as correction information,the correction information is referred to as stage position inducederror correction information.

Next, a calibration process of a head position (measurement beamposition) for acquiring a position coordinate of each head (or to bemore precise, the measurement beam emitted from each head) in the XYplane, especially the position coordinate in the direction besides themeasurement direction, which becomes a premise in processes such as aprocess to convert the measurement value of an encoder to be describedlater into positional information of wafer stage WST in the XY plane anda linkage process among a plurality of encoders, will be described. Inthis case, as an example, a calibration process of the positioncoordinate in the direction besides the measurement direction (theX-axis direction) orthogonal to the measurement direction of themeasurement beam emitted from Y head 64 configuring each head unit 62Aand 62C will be described.

First of all, on starting this calibration processing, main controller20 drives wafer stage WST and moves Y scales 39Y₁ and 39Y₂ so that Yscales 39Y₁ and 39Y₂ are located under head units 62A and 62C,respectively. For example, as shown in FIG. 14, Y head 64 _(A3), whichis the third head from the left of head unit 62A, and Y head 64 _(C5),which is the second head from the right of head unit 62C, are made toface Y scales 39Y₁ and 39Y₂, respectively.

Next, based on the measurement values of measurement beams B4₁ and B4₂of Y interferometer 16, or the measurement values of Z interferometers43A and 43B, main controller 20 rotates wafer stage WST only by apredetermined angle (the angle being θ) within the XY plane with opticalaxis AX of projection optical system PL serving as a center as shown byan arrow RV in FIG. 14, and acquires the measurement values of Y heads64 _(A3) and 64 _(C5) (encoders 70A and 70C), which can be obtainedduring the rotation. In FIG. 14, vectors MA and MB, which correspond tothe measurement values measured during the rotation of wafer stage WSTby Y heads 64 _(A3) and 64 _(C5), are respectively shown.

In this case, because θ is a very small angle, MA=b/θ and MB=a/θ arevalid, and a ratio MA/MB of the magnitude of vectors MA and MB are equalto a ratio a/b, which is a ratio of the distance from the rotationcenter to the irradiation point (also referred to as a detection pointof the encoder of the head) of each measurement beam emitted from Yheads 64 _(A3) and 64 _(C5), respectively.

Therefore, main controller 20 computes distances b and a, or morespecifically, the X-coordinate values of the irradiation points of themeasurement beams emitted from Y heads 64 _(A3) and 64 _(C5), based onpredetermined angle θ obtained from the measurement values of encoders70A and 70C and the measurement values of interferometer beams B4₁ andB4₂, respectively, or, furthermore performs a calculation based on theX-coordinate values that have been computed, and computes the positionalshift amount (more specifically, correction information of thepositional shift amount) of the irradiation points of the measurementbeams emitted from Y heads 64 _(A3) and 64 _(C5), respectively, in theX-axis direction with respect to the design position.

Further, in the case wafer stage WST is located at the position shown inFIG. 14, in actual practice, head units 62B and 62D face X scales 39X₁and 39X₂, respectively. Accordingly, on the rotation of wafer stage WSTdescribed above, main controller 20 simultaneously acquires themeasurement values of each X head 66 (encoders 70B and 70D) of headunits 62B and 62D that respectively face X scales 39X₁ and 39X₂. Then,in a manner similar to the description above, main controller 20computes the Y-coordinate values of the irradiation point of themeasurement beams emitted from X head 66, respectively, which each faceX scale 39X₁ and 39X₂, or, furthermore performs a calculation based onthe computation results, and computes the positional shift amount (morespecifically, correction information of the positional shift amount) ofthe irradiation point of the measurement beams emitted from therespective X heads in the Y-axis direction with respect to the designposition.

Next, main controller 20 moves wafer stage WST in the X-axis directionat a predetermined pitch, and by performing a processing similar to theprocedure described above at each positioning position, main controller20 can obtain the X-coordinate values of the irradiation point of themeasurement beams emitted from the heads, or the positional shift amount(more specifically, correction information of the positional shiftamount) in the X-axis direction with respect to the design position alsofor the remaining Y heads of head units 62A and 62C.

Further by moving in the Y-axis direction at a predetermined pitch fromthe position shown in FIG. 14 and performing a processing similar to theprocedure described above at each positioning position, main controller20 can obtain the Y-coordinate values of the irradiation point of themeasurement beams emitted from the heads or the positional shift amount(more specifically, correction information of the positional shiftamount) in the Y-axis direction with respect to the design position,also for the remaining X heads of head units 62B and 62D.

Further, in a method similar to Y head 64 described above, maincontroller 20 acquires the X-coordinate values of the irradiation pointof the measurement beam emitted from the heads or the positional shiftamount (more specifically, correction information of the positionalshift amount) in the X-axis direction with respect to the designposition, also for Y heads 64 y ₁ and y₂.

In the manner described above, main controller 20 can acquire theX-coordinate values of the irradiation point of the measurement beamemitted from the heads or the positional shift amount (morespecifically, correction information of the positional shift amount) inthe X-axis direction with respect to the design position for all Y heads64, 64 y ₁, and 64 y ₂, and the Y-coordinate values of the irradiationpoint of the measurement beam emitted from the heads or the positionalshift amount (more specifically, correction information of thepositional shift amount) in the Y-axis direction with respect to thedesign position also for all X heads 66, therefore, the information thathas been acquired is stored in a storage unit, such as, for example,memory 34. The X-coordinate values or the Y coordinate values of theirradiation point of the measurement beam of each head or the positionalshift amount in the X-axis direction or the Y-axis direction withrespect to the design position of each head stored in memory 34, will beused such as when converting the measurement values of an encoder intopositional information within the XY plane of wafer stage WST, as itwill be described later on. Incidentally, on converting the measurementvalues of an encoder into positional information within the XY plane ofwafer stage WST or the like described later on, design values are usedfor the Y coordinate values of the irradiation point of the measurementbeam of each Y head, and the X-coordinate values of the irradiationpoint of the measurement beam of each X head. This is because since theinfluence that the position coordinates of each head in the measurementdirection has on the control accuracy of the position of wafer stage WSTis extremely weak, (the effectiveness to the control accuracy isextremely slow), it is sufficient enough to use the design values.

Now, when there is an error (or a gap) between the height (the Zposition) of each scale surface (the grating surface) on wafer table WTBand the height of a reference surface including the exposure center (itis the center of exposure area IA previously described and coincideswith optical axis AX of projection optical system PL in the embodiment),the so-called Abbe error occurs in the measurement values of the encoderon rotation (pitching or rolling) around an axis (an X-axis or a Y-axis)parallel to the XY plane of wafer stage WST, therefore, this error needsto be corrected. The reference surface, here, is a surface which is areference for displacement ΔZo of wafer stage WST in the Z-axisdirection measured with interferometer system 118, and refers to asurface (in the embodiment, the surface coincides with the image planeof projection optical system PL) which is a reference for alignment(position control) of each shot area on wafer W in the Z-axis direction.

For the correction of the error described above, it is necessary toaccurately obtain the difference of height (the so-called Abbe offsetquantity) of each scale surface (the grating surface) with respect tothe reference surface of wafer stage WST. This is because correcting theAbbe errors due to the Abbe offset quantity described above is necessaryin order to accurately control the position of wafer stage WST withinthe XY plane using an encoder system. By taking into consideration suchpoints, in the embodiment, main controller 20 performs calibration forobtaining the Abbe offset quantity described above in the followingprocedure.

First of all, on starting this calibration processing, main controller20 drives wafer stage WST and moves Y scales 39Y₁ and 39Y₂ so that Yscales 39Y₁ and 39Y₂ are located under head units 62A and 62C,respectively. In this case, for example, as shown in FIG. 15, Y head 64_(A3) being the third head from the left of head unit 62A faces area ARwhich is a specific area on Y scale 39Y₁ where Y head 64 _(A3) had facedwhen acquiring the stage position induced error correction informationin the previous description. Further, in this case, as shown in FIG. 15,Y head 64 _(C4) being the fourth head from the left of head unit 62Cfaces an area which is a specific area on Y scale 39Y₂ where Y head 64_(C4) had faced when acquiring the stage position induced errorcorrection information in the previous description.

Next, based on measurement results of Y interferometer 16 which usesmeasurement beams B4₁, B4₂ and B3 previously described, main controller20 tilts wafer stage WST around an axis that passes the exposure centerand is parallel to the X-axis so that pitching amount Δθx becomes zeroin the case displacement (pitching amount) Δθx of wafer stage WST in theθx direction with respect to the XY plane is not zero, based on themeasurement results of Y interferometer 16 of interferometer system 118.Because all the corrections of each interferometer of interferometersystem 118 have been completed at this point, such pitching control ofwafer stage WST becomes possible.

Then, after such adjustment of the pitching amount of wafer stage WST,main controller 20 acquires measurement values y_(A0) and y_(C0) ofencoders 70A and 70C, configured by Y scales 39Y₁ and 39Y₂ and Y heads64 _(A3) and 64 _(C4) that face Y scales 39Y₁ and 39Y₂, respectively.

Next, main controller 20 tilts wafer stage WST at an angle φ around theaxis that passes the exposure center and is parallel to the X-axis,based on measurement results of Y interferometer 16 which usesmeasurement beams B4₁, B4₂ and B3, as shown by arrow RX in FIG. 15.Then, main controller 20 acquires measurement values y_(A1) and y_(C1)of encoders 70A and 70C, configured by Y scales 39Y₁ and 39Y₂ and Yheads 64 _(A3) and 64 _(C4) that face Y scales 39Y₁ and 39Y₂,respectively.

Then, based on measurement values y_(A0), y_(C0), and y_(A1), y_(C1) ofencoders 70A and 70C acquired above, and angle φ above, main controller20 computes the so-called Abbe offset quantities h_(A) and h_(C) of Yscales 39Y₁ and 39Y₂. In this case, because φ is a very small angle, sinφ=φ and cos φ=1 are valid.

h _(A)=(y _(A1) −y _(A0))  (12)

h _(C)=(y _(C1) −y _(C0))  (13)

Next, after adjusting the pitching amount of wafer stage WST so thatpitching amount Δθx becomes zero, main controller 20 drives wafer stageWST if necessary in the X-axis direction, and makes a predetermined Xhead 66 of head units 62B and 62D face the specific area on X scales39X₁ and 39X₂ where each X head 66 had faced when acquiring the stageposition induced error correction information in the previousdescription.

Next, main controller 20 performs a calculation of formula (6)previously described, using the output of Z interferometers 43A and 43Bpreviously described, and in the case displacement (rolling amount) Δθyof wafer stage WST in the θy direction with respect to the XY plane isnot zero, main controller 20 tilts wafer stage WST around an axis thatpasses the exposure center and is parallel to the Y-axis so that rollingamount My becomes zero. Then, after such adjustment of the rollingamount of wafer stage WST, main controller 20 acquires measurementvalues x_(B0) and x_(D0) of encoders 70B and 70D, configured by X scales39X₁ and 39X₂ and each X head 66, respectively.

Next, main controller 20 tilts wafer stage WST at angle φ around theaxis that passes the exposure center and is parallel to the Y-axis,based on the output of Z interferometers 43A and 43B, and acquiresmeasurement values x_(B1) and x_(D1) of encoders 70B and 70D, configuredby X scales 39X₁ and 39X₂ and each X head 66, respectively.

Then, based on measurement values X_(B0), X_(D0), and X_(B1), X_(D1) ofencoders 70B and 70D acquired above, and angle φ above, main controller20 computes the so-called Abbe offset quantities h_(B) and h_(D) of Xscales 39X₁ and 39X₂. In this case, φ is a very small angle.

h _(B)=(x _(B1) −x _(B0))/φ  (14)

h _(D)=(x _(D1) −x _(D0))/φ  (15)

As it can be seen from formulas (12) and (13) above, when the pitchingamount of wafer stage WST is expressed φx, then Abbe errors ΔA_(A) andΔA_(C) of Y encoders 70A and 70C that accompany the pitching of waferstage WST can be expressed as in the following formulas (16) and (17).

ΔA _(A) =h _(A) *φx  (16)

ΔA _(C) =h _(C) *φx  (17)

Similarly, as it can be seen from formulas (14) and (15) above, when therolling amount of wafer stage WST is expressed φy, then Abbe errorsΔA_(B) and ΔA_(D) of X encoders 70B and 70D that accompany the rollingof wafer stage WST can be expressed as in the following formulas (18)and (19).

ΔA _(B) =h _(B) *φy  (18)

ΔA _(D) =h _(D) *φy  (19)

Main controller 20 stores the quantities h_(A) to h_(p) or formulas (16)to (19) obtained in the manner described above in memory 34.Accordingly, on the actual position control of wafer stage WST such asduring lot processing and the like, main controller 20 is able to drive(perform position control of) wafer stage WST with high precision in anarbitrary direction within the XY plane while correcting the Abbe errorsincluded in the positional information of wafer stage WST within the XYplane (the movement plane) measured by the encoder system, or, morespecifically, measurement errors of Y encoders 70A and 70C correspondingto the pitching amount of wafer stage WST caused by the Abbe offsetquantities of the surface of Y scales 39Y₁ and 39Y₂ (the gratingsurface) with respect to the reference surface previously described, ormeasurement errors of X encoders 70B and 70D corresponding to therolling amount of wafer stage WST caused by the Abbe offset quantitiesof the surface of X scales 39X₁ and 39X₂ (the grating surface) withrespect to the reference surface previously described. Incidentally, inthe embodiment, the position of wafer stage WST in the Z-axis, the θxand the θy directions is controlled so that the surface of wafer Wsubstantially coincides with the image plane (the reference surface) ofprojection optical system PL at the time of exposure. Furthermore, waferW is held so that its surface is substantially flush with the uppersurface of wafer stage WST, and the scale has a cover glass arranged onits grating surface whose surface is substantially flush with the uppersurface and the surface of wafer stage WST. Accordingly, the Abbe offsetquantity of the scale to the image plane of projection optical system PLis almost equal to the distance (that is, almost equal to the thicknessof the cover glass) between the grating surface of the scale and theupper surface of wafer stage WST in the Z-axis direction.

Now, in the case the optical axis of the heads of the encodersubstantially coincides with the Z-axis, and the pitching amount,rolling amount, and yawing amount of wafer stage WST are all zero, as itis obvious from formulas (10) and (11) above, measurement errors of theencoder described above due to the attitude of wafer table WTB are notsupposed to occur, however, even in such a case, the measurement errorsof the encoder are not actually zero. This is because the surface of Yscales 39Y₁ and 39Y₂, and X scales 39X₁ and 39X₂ (the surface of thesecond water repellent plate 28 b) is not an ideal plane, and issomewhat uneven. When the surface of the scale (to be more precise, thediffraction grating surface, and including the surface of a cover glassin the case the diffraction grating is covered with the cover glass) isuneven, the scale surface will be displaced in the Z-axis direction(move vertically), or be inclined with respect to the heads of theencoder even in the case when wafer stage WST moves along a surfaceparallel to the XY plane. This consequently means none other that arelative motion occurs in the non-measurement direction between the headand the scale, and as it has already been described, such a relativemotion becomes a cause of the measurement error.

Further, as shown in FIG. 16, for example, in the case of measuring aplurality of measurement points P₁ and P₂ on the same scale 39X using aplurality of heads 66A and 66B, when the tilt of the optical axis of theplurality of heads 66A and 66B is different and there is also anunevenness (including inclination) to the surface of scale 39X, as isobvious from ΔX_(A)≠ΔX_(B) shown in FIG. 16, the influence that theunevenness has on the measurement values will differ for each headdepending on the tilt difference. Accordingly, in order to remove suchdifference in the influence, it will be necessary to obtain theunevenness of the surface of scale 39X. The unevenness of the surface ofscale 39X may be measured, for example, using a measurement unit besidesthe encoder such as the Z sensor previously described, however, in sucha case, because the measurement accuracy of the unevenness is setaccording to the measurement resolution of the measurement unit, inorder to measure the unevenness with high precision, a possibility mayoccur of having to use a sensor that has a higher precision and is morecostly than the sensor necessary to fulfill the original purpose as a Zsensor.

Therefore, in the embodiment, a method of measuring the unevenness ofthe surface of a scale using the encoder system itself is employed.Following is a description of the method.

As shown in a graph (an error characteristics curve) of FIG. 12, whichshows a change characteristic of the measurement values of the encoder(a head) corresponding to the Z leveling of wafer stage WST previouslydescribed, only one point can be found in the Z-axis direction for eachencoder head where the head has no sensibility to the tilt operation ofwafer stage WST, or more specifically, a singular point where themeasurement error of the encoder becomes zero regardless of the angle ofinclination of wafer stage WST to the XY plane. If this point can befound by moving wafer stage WST similarly as when acquiring the stageposition induced error correction information previously described, thepoint (a Z position) can be positioned the singular point with respectto the encoder head. If such operation to find the singular point isperformed on a plurality of measurement points on the scale, the shape(unevenness) of the surface of the scale can be obtained.

(a) Therefore main controller 20 first of all drives wafer stage WST viastage drive system 124, while monitoring the measurement values of Yinterferometer 16 of interferometer system 118, X interferometer 126,and Z interferometers 43A and 43B, and as shown in FIG. 17, makes anarbitrary Y head of head unit 62A, such as for example, Y head 64 _(A2)in FIG. 17, face the vicinity of the end section of Y scale 39Y₁ on the+Y side. Then, main controller 20 changes the pitching amount (θxrotation quantity) of wafer stage WST at the position in at least twostages as is previously described, and in a state where the attitude ofwafer stage WST at the time of change is maintained for every change,main controller 20 scans (moves) wafer stage WST in the Z-axis directionin a predetermined stroke range while irradiating a detection light on apoint of Y scale 39Y₁ subject to measurement from Y head 64, and samplesthe measurement results of Y head 64 _(A2) (encoder 70A) that faces Yscale 39Y₁ during the scan (movement). Incidentally, the sampling aboveis performed while maintaining the yawing amount (and rolling amount) ofwafer stage WST at zero.

Then, by performing a predetermined operation based on the samplingresults, main controller 20 obtains an error characteristics curve(refer to FIG. 12) at the point described above subject to themeasurement of encoder 70A corresponding to the Z position of waferstage WST for a plurality of attitudes, and sets the intersecting pointof the plurality of error characteristics curves, or more specifically,sets the point where the measurement error of encoder 70A above becomeszero regardless of the angle of inclination of wafer stage WST withrespect to the XY plane as the singular point at the measurement point,and obtains Z positional information z₁ (refer to FIG. 18A) of thesingular point.

(b) Next, main controller 20 steps wafer stage WST in the +Y directionby a predetermined amount via stage drive system 124 while maintainingthe pitching amount and rolling amount of wafer stage WST at zero, whilemonitoring the measurement values of Y interferometer 16 ofinterferometer system 118, X interferometer 126, and Z interferometers43A and 43B. This step movement is performed at a speed slow enough sothat measurement errors caused by air fluctuation of the interferometerscan be ignored.

(c) Then, at a position after the step movement, as in (a) above, maincontroller 20 obtains a Z positional information z_(p) (in this case,p=2) of the singular point of encoder 70A above at the position.

After this operation, by repeating the operations similar to the onesdescribed in (b) and (c) above, main controller 20 obtains a Zpositional information z_(p) (p=2,3, i, k, n) in a plurality of (e. g.n−1) measurement points set at a predetermined interval in the Y-axisdirection on scale 39Y₁.

FIG. 18B shows a z positional information z_(i) of the singular point atthe i^(th) measurement point that was obtained in the manner describedabove, and FIG. 18C shows a z positional information z_(k) of thesingular point at the k^(th) measurement point.

(d) Then, based on Z positional information z₁, z₂, . . . z_(n) of thesingular point obtained for each of the plurality of measurement pointsabove, main controller 20 obtains the unevenness of the surface of scale39Y₁. As shown in FIG. 18D, if one end of a double-sided arrow showing Zposition z_(p) of the singular point in each measurement point on scale39Y₁ is made to coincide with a predetermined reference line, the curvewhich links the other end of each double-sided arrow indicates the shapeof the surface (unevenness) of scale 39Y₁. Accordingly, main controller20 obtains function z=f₁(y) that expresses this unevenness by performingcurve fitting (a least square approximation) on the point at the otherend of each double-sided arrow, and is stored in memory 34.Incidentally, y is a Y-coordinate of wafer stage WST measured with Yinterferometer 16.

(e) In a similar manner described above, main controller 20 obtainsfunction z=f₂(y) that expresses the unevenness of Y scale 39Y₂, functionz=g₁(x) that expresses the unevenness of X scale 39X₁, and, functionz=g₂(x) that expresses the unevenness of X scale 39X₂, respectively, andstores them in memory 34. Incidentally, x is an X-coordinate of waferstage WST measured with X interferometer 126.

In this case, at each measurement point on each scale, when an errorcharacteristics curve whose measurement error always becomes zero isobtained regardless of the change of Z in the case of obtaining theerror characteristics curve (refer to FIG. 12) described above, thepitching amount (or rolling amount) of wafer stage WST at the point whenthe error characteristics curve was obtained corresponds to an inclinedquantity of the scale surface at the measurement point. Accordingly, inthe method above, information on inclination at each measurement pointcan also be obtained, in addition to the height information of the scalesurface. This arrangement allows fitting with higher precision when thecurve fitting described above is performed.

Now, the scale of the encoder lacks in mechanical long-term stability,such as in the diffraction grating deforming due to thermal expansion orother factors by the passage of use time, or the pitch of thediffraction grating changing partially or entirely. Therefore, becausethe errors included in the measurement values grow larger with thepassage of use time, it becomes necessary to correct the errors.Hereinafter, an acquisition operation of correction information of thegrating pitch and of correction information of the grating deformationperformed in exposure apparatus 100 of the embodiment will be described,based on FIG. 19.

In FIG. 19, measurement beams B4₁ and B4₂ are arranged symmetric tostraight line LV previously described, and the substantial measurementaxis of Y interferometer 16 coincides with straight line LV, whichpasses through the optical axis of projection optical system PL and isparallel to the Y-axis direction. Therefore, according to Yinterferometer 16, the Y position of wafer table WTB can be measuredwithout Abbe error. Similarly, measurement beams B5₁ and B5₂ arearranged symmetric to straight line LH previously described, and thesubstantial measurement axis of X interferometer 126 coincides withstraight line LH, which passes through the optical axis of projectionoptical system PL and is parallel to the X-axis direction. Therefore,according to X interferometer 126, the X position of wafer table WTB canbe measured without Abbe error.

First of all, an acquisition operation of correction information of thedeformation (curve of the grid line) of the grid line of the X scale,and correction information of the grating pitch of the Y scale will bedescribed. In this case, to simplify the description, reflection surface17 b is to be an ideal plane. Further, prior to this acquisitionoperation, a measurement of the unevenness information of the surface ofeach scale described above is performed, and function z=f₁(y) thatexpresses the unevenness of Y scale 39Y₁, function z=f₂(y) thatexpresses the unevenness of Y scale 39Y₂, function z=g₁(x) thatexpresses the unevenness of X scale 39X₁, and function z=g₂(x) thatexpresses the unevenness of X scale 39X₂, are to be stored in memory 34.

First of all, main controller 20 reads function z=f₁(y), functionz=f₂(y), function z=g_(r)(x) and function z=g₂(x) stored in memory 34into the internal memory.

Next, at a speed low enough so that the short-term variation of themeasurement values of Y interferometer 16 can be ignored and also in astate where the measurement value of X interferometer 126 is fixed to apredetermined value, main controller 20 moves wafer stage WST based onthe measurement values of Y interferometer 16, and Z interferometers 43Aand 43B, for example, in at least one direction of the +Y direction andthe −Y-direction with in the effective stroke range mentioned earlier asis indicated by arrow F and F′ in FIG. 19, in a state where the pitchingamount, the rolling amount, and the yawing amount are all maintained atzero. During this movement, while correcting the measurement values (theoutput) of Y linear encoders 70A and 70C using the function z=f₁(y) andfunction z=f₂(y) described above, respectively, main controller 20 takesin the measurement values after the correction and the measurementvalues (or to be more precise, measurement values of measurement beamsB4₁ and B4₂) of Y interferometer 16 at a predetermined samplinginterval, and based on each measurement value that has been taken in,obtains a relation between the measurement values of Y linear encoders70A and 70C (output of encoder 70A—the measurement values correspondingto function f₁(y), output of encoder 70C—the measurement valuescorresponding to function f₂(y)) and the measurement values of Yinterferometer 16. More specifically, in the manner described above,main controller 20 obtains a grating pitch (the distance betweenadjacent grid lines) of Y scales 39Y₁ and 39Y₂ which are sequentiallyplaced opposing head units 62A and 62C with the movement of wafer stageWST and correction information of the grating pitch. As the correctioninformation of the grating pitch, for example, in the case a horizontalaxis shows the measurement values of the interferometer and a verticalaxis shows the measurement values (the measurement values whose errorsdue to the unevenness of the scale surface has been corrected) of theencoder, a correction map which shows the relation between the two usinga curve can be obtained. Because the measurement values of Yinterferometer 16 in this case are obtained when wafer stage WST wasscanned at an extremely low speed as was previously described, themeasurement values hardly include any short-term variation errors due toair fluctuation, as well as long-term variation errors, and it can besaid that the measurement values are accurate values in which the errorscan be ignored.

Further, during the movement of wafer stage WST described above, bystatistically processing the measurement values (the measurement valuesof X linear encoders 70B and 70D) obtained from a plurality of X heads66 of head units 62B and 62D placed sequentially opposing X scales 39X₁and 39X₂ with the movement, such as, for example, averaging (orperforming weighted averaging), main controller 20 also obtainscorrection information of the deformation (warp) of grid lines 37 whichsequentially face the plurality of X heads 66. This is because in thecase reflection surface 17 b is an ideal plane, the same blurringpattern should appear repeatedly in the process when wafer stage WST issent in the +Y direction or the −Y-direction, therefore, if averaging orthe like is performed on the measurement data acquired with theplurality of X heads 66, it becomes possible to precisely obtaincorrection information of the deformation (warp) of grid lines 37 whichsequentially face the plurality of X head 66.

Incidentally, in a normal case where reflection surface 17 b is not anideal plane, by measuring the unevenness (warp) of the reflectionsurface and obtaining the correction data of the warp in advance andperforming movement of wafer stage WST in the +Y direction or the−Y-direction while controlling the X position of wafer stage WST, basedon the correction data instead of fixing the measurement value of Xinterferometer 126 to the predetermined value on the movement of waferstage WST in the +Y direction or the −Y-direction described above, waferstage WST can be made to move precisely in the Y-axis direction. In thismanner, the same correction information of the grating pitch of the Yscale and the correction information of the deformation (warp) of gridlines 37 can be obtained as in the description above. Incidentally, themeasurement data acquired with the plurality of X heads 66 describedabove is a plurality of data at different location references ofreflection surface 17 b, and because X heads 66 measure deformation(warp) of the same grid line 37, there is a collateral effect of thewarp correction residual of the reflection surface being averaged andapproaching its true value (in other words, by averaging the measurementdata (warp information of grid line 37) acquired by the plurality of Xheads, the effect of the warp residual can be weakened) by the averagingor the like described above.

Next, acquisition operations of correction information of deformation(warp of the grid lines) of the grid lines of the Y scale and correctioninformation of the grating pitch of the X scale will be described. Inthis case, to simplify the description, reflection surface 17 a is to bean ideal plane. In this case, a processing as in the case of thecorrection described above, but with the X-axis direction and the Y-axisdirection interchanged, should be performed.

More specifically, at a speed low enough so that the short-teenvariation of the measurement values of X interferometer 126 can beignored and also in a state where the measurement value of Yinterferometer 16 is fixed to a predetermined value, main controller 20moves wafer stage WST based on the measurement values of Yinterferometer 16, and Z interferometers 43A and 43B, for example, in atleast one direction of the +X direction and the −X direction with in theeffective stroke range mentioned earlier, in a state where the pitchingamount, the rolling amount, and the yawing amount are all maintained atzero. During this movement, while correcting the measurement values of Xlinear encoders 70B and of 70D using the function z=g₁(x) and functionz=g₂(x) described above, respectively, main controller 20 takes in themeasurement values after the correction and the measurement values of Xinterferometer 126 at a predetermined sampling interval, and based oneach measurement value that has been taken in, obtains a relationbetween the measurement values of X linear encoders 70B and 70D (outputof encoder 70B—the measurement values corresponding to function g₁(x),output of encoder 70D—the measurement values corresponding to functiong₂(x)) and the measurement values of X interferometer 126. Morespecifically, in the manner described above, main controller 20 obtainsa grating pitch (the distance between adjacent grid lines) of X scales39X₁ and 39X₂ which are sequentially placed opposing head units 62B and62D with the movement of wafer stage WST and the correction informationof the grating pitch. As the correction information of the gratingpitch, for example, in the case a horizontal axis shows the measurementvalues of the interferometer and a vertical axis shows the measurementvalues (the measurement values whose errors due to the unevenness of thescale surface has been corrected) of the encoder, a map which shows therelation between the two using a curve can be obtained. Because themeasurement values of X interferometer 126 in this case are obtainedwhen wafer stage WST was scanned at an extremely low speed as waspreviously described, the measurement values hardly include anyshort-term variation errors due to air fluctuation, as well as long-termvariation errors, and it can be said that the measurement values areaccurate values in which the errors can be ignored.

Further, during the movement of wafer stage WST described above, bystatistically processing the measurement values (the measurement valuesof Y linear encoders 70A and 70C) obtained from a plurality of Y heads64 of head units 62A and 62C placed sequentially opposing Y scales 39Y₁and 39Y₂ with the movement, such as, for example, averaging (orperforming weighted averaging), main controller 20 also obtainscorrection information of the deformation (warp) of grid lines 38 whichsequentially face the plurality of Y heads 64. This is because in thecase reflection surface 17 a is an ideal plane, the same blurringpattern should appear repeatedly in the process when wafer stage WST issent in the +X direction or the −X-direction, therefore, if averaging orthe like is performed on the measurement data acquired with theplurality of Y heads 64, it becomes possible to precisely obtaincorrection information of the deformation (warp) of grid lines 38 whichsequentially face the plurality of Y head 64.

Incidentally, in a normal case where reflection surface 17 a is not anideal plane, by measuring the unevenness (warp) of the reflectionsurface and obtaining the correction data of the warp in advance andperforming movement of wafer stage WST in the +X direction or the −Xdirection while controlling the Y position of wafer stage WST, based onthe correction data instead of fixing the measurement value of Yinterferometer 16 to the predetermined value on the movement of waferstage WST in the +X direction or the −X direction described above, waferstage WST can be made to move precisely in the Y-axis direction. In thismanner, the same correction information of the grating pitch of the Xscale and the correction information of the deformation (warp) of gridlines 38 can be obtained as in the description above.

As is described above, main controller 20 obtains correction informationon grating pitch of the Y scales and correction information ondeformation (warp) of grating lines 37, and correction information ongrating pitch of the X scales and correction information on deformation(warp) of grating lines 38 at each predetermined timing, for example,with respect to each lot, or the like.

And, during processing of the lot, main controller 20 performs movementcontrol of wafer stage WST in the Y-axis direction, using Y scales 39Y₁and 39Y₂ and head units 62A and 62C, or more specifically, using Ylinear encoders 70A and 70C, while correcting the measurement valuesobtained from head units 62A and 62C (more specifically, the measurementvalues of encoders 70A and 70C), based on correction information of thegrating pitch and correction information of the deformation (warp) ofgrid line 38 referred to above, stage position induced error correctioninformation corresponding to the Z position of wafer stage WST measuredby interferometer system 118, pitching amount Δθx, and yawing amountΔθz, and correction information of the Abbe error that corresponds topitching amount Δθx of wafer stage WST caused by the Abbe offsetquantity of the surface of Y scales 39Y₁ and 39Y₂. By this operation, itbecomes possible for main controller 20 to perform movement control ofwafer stage WST in the Y-axis direction with good precision using Ylinear encoders 70A and 70C, without being affected by temporal changeof the grating pitch of the Y scale and the warp of each grating (line)that make up the Y scale, without being affected by the change ofposition of wafer stage WST in the direction besides the measurementdirection (relative motion between the head and the scale in thedirection besides the measurement direction), and without being affectedby the Abbe error.

Further, during processing of the lot, main controller 20 performsmovement control of wafer stage WST in the X-axis direction, using Xscales 39X₁ and 39X₂ and head units 62B and 62D, or more specifically,using X linear encoders 70B and 70D, while correcting the measurementvalues obtained from head units 62B and 62D (more specifically, themeasurement values of encoders 70B and 70D), based on correctioninformation of the grating pitch and correction information of thedeformation (warp) of grid line 37 referred to above, stage positioninduced error correction information corresponding to the Z position ofwafer stage WST measured by interferometer system 118, rolling amountθy, and yawing amount θz, and correction information of the Abbe errorthat corresponds to rolling amount Δθy of wafer stage WST caused by theAbbe offset quantity of the surface of X scales 39X₁ and 39X₂. By thisoperation, it becomes possible for main controller 20 to performmovement control of wafer stage WST in the X-axis direction with goodprecision using X linear encoders 70B and 70D, without being affected bytemporal change of the grating pitch of the X scale and the warp of eachgrating (line) that make up the X scale, without being affected by thechange of position of wafer stage WST in the non-measurement direction(relative motion between the head and the scale in the non-measurementdirection), and without being affected by the Abbe error.

Incidentally, in the description above, the case has been describedwhere the correction information of the grating pitch and the grid linewarp was acquired for both the Y scale and the X scale, however, thepresent invention is not limited to this, and the correction informationof the grating pitch and the grid line warp can be acquired only foreither the Y scale or the X scale, or the correction information of onlyeither the grating pitch or the grid line warp can be acquired for boththe Y scale and the X scale. For example, in the case where only theacquisition of the correction information of the warp of grid line 37 ofthe X scale is performed, wafer stage WST can be moved in the Y-axisdirection based on the measurement values of Y linear encoders 70A and70C, without necessarily using Y interferometer 16. Similarly, in thecase where only the acquisition of the correction information of thewarp of grid line 38 of the Y scale is performed, wafer stage WST can bemoved in the X-axis direction based on the measurement values of Xlinear encoders 70B and 70D, without necessarily using X interferometer126. Further, either one of the stage position induced error previouslydescribed or the measurement error (hereinafter also referred to as ascale induced error) of the encoder which occurs due to the scale (forexample, degree of flatness of the grating surface (surface smoothness)and/or grating formation error (including pitch error, grid line warpand the like) can be compensated.

Next, a switching process of the encoder used for position control ofwafer stage WST in the XY plane that is executed during the actualprocessing or the like, or more specifically, a linkage process betweena plurality of encoders will be described, after processing such as theacquisition of the stage position induced error correction information,unevenness measurement of the surface of the scale, the acquisition ofcorrection information of the grating pitch of the scale and thecorrection information of the grating deformation, and the acquisitionof the Abbe offset quantity of the scale surface and the like areperformed in advance.

In this case, first of all, prior to describing the linkage process ofthe plurality of encoders, a concrete method of converting the correctedmeasurement values of the encoder into the position of wafer stage WST,which is the premise, will be described, using FIGS. 20A and 20B. Inthis case, in order to simplify the description, the degrees of freedomof wafer stage WST is to be three degrees of freedom (X, Y, and θz).

FIG. 20A shows a reference state where wafer stage WST is at the originof coordinates (X, Y, θz)=(0,0,0). From this reference state, waferstage WST is driven in a range where encoders (Y heads) Enc1 and Enc2and encoder (X head) Enc3 do not move away from the scanning areas oftheir opposing scales 39Y₁, 39Y₂ and 39X₁. The state where wafer stageWST is moved to position (X, Y, θz) in the manner described above isshown in FIG. 20B.

Here, let position coordinates (X, Y) of the measurement points ofencoders Enc1, Enc2, and Enc3 on the XY coordinate system be (p₁, q₁),(p₂, q₂), and (p₃, q₃), respectively. The positional information whichwas acquired in the case of the calibration of the head positiondescribed earlier is read from memory 34 and used for X-coordinatevalues p₁ and q₂ of encoders Enc1 and Enc2 and Y coordinate value p₃ ofencoder Enc3, and the design positional information of the irradiationpoint of the measurement beam is read from memory 34 and used for Ycoordinate values q₁ and q₂ of encoders Enc1 and Enc2 and X-coordinatevalue p₃ of encoder Enc3.

The X head and the Y head respectively measure the relative distancefrom central axes LL and LW of wafer stage WST. Accordingly, measurementvalues C_(X) and C_(Y) of the X head and the Y head can be expressed,respectively, as in the following formulas (20a) and (20b).

C _(X) =r′*ex′  (20a)

C _(Y) =r′*ey′  (20b)

In this case, ex′ and ey′ are X′ and Y′ unit vectors in a relativecoordinate system (X′, Y′, θz′) set on wafer stage WST, and have arelation as in the following Y formula (21) with X and Y unit vectors exand ey in the reference coordinate system (X, Y, θz).

$\begin{matrix}{\begin{pmatrix}{ex}^{\prime} \\{ey}^{\prime}\end{pmatrix} = {\begin{pmatrix}{\cos \; \theta \; z} & {\sin \; \theta \; z} \\{{- \sin}\; \theta \; z} & {\cos \; \theta \; z}\end{pmatrix}\begin{pmatrix}{ex} \\{ey}\end{pmatrix}}} & (21)\end{matrix}$

Further, r′ is a position vector of the encoder in the relativecoordinate system, and r′ is given r′=r−(O′−O), using position vectorr=(p, q) in the reference coordinate system. Accordingly, formulas (20a)and (20b) are rewritten as in formulas (22a) and (22b) below.

C _(X)=(p−X)cos θz+(q−Y)sin θz  (22a)

C _(Y)=−(p−X)sin θz+(q−Y)cos θz  (22b)

Accordingly, when wafer stage WST is located at the coordinate (X, Y,θz) as shown in FIG. 20B, the measurement values of three encoders canbe expressed theoretically as in the next formulas (23a) to (23c) (alsoreferred to as a relationship of the affine transformation).

C ₁=−(p ₁ −X)sin θz+(q ₁ −Y)cos θz  (23a)

C ₂=−(p ₂ −X)sin θz+(q ₂ −Y)cos θz  (23b)

C ₃=(p ₃ −X)cos θz+(q ₃ −Y)sin θz  (23c)

Incidentally, in the reference state of FIG. 20A, according tosimultaneous equations (23a) to (23c), C₁=q₁, C₂=q₂, and C₃=p₃.Accordingly, in the reference state, if the measurement values of thethree encoders Enc1, Enc2, and Enc3 are initialized to q₁, q₂, and p₃respectively, then the three encoders will show theoretical values givenby formulas (23a) to (23c) with respect to displacement (X, Y, θz) ofwafer stage WST from then onward.

In simultaneous equations (23a) to (23c), three formulas are given tothe three variables (X, Y, θz). Accordingly, if dependent variables C₁,C₂, and C₃ are given in the simultaneous equations (23a) to (23c),variables X, Y, and θz can be obtained. In this case, when approximationsin θz θz is applied, or even if an approximation of a higher order isapplied, the equations can be solved easily. Accordingly, the positionof wafer stage WST (X, Y, θz) can be computed from measurement valuesC₁, C₂, and C₃ of the encoder.

Next, a linkage process performed during the switching of the encoderhead used for position control of wafer stage WST in the XY plane in theembodiment, or more specifically, an initial setting of a measurementvalue will be described, focusing on an operation of main controller 20.

In the embodiment, as is previously described, three encoders (the Xheads and the Y heads) constantly observe wafer stage WST within theeffective stroke range of wafer stage WST, and when the switchingprocess of the encoder is performed, four encoders will be made toobserve wafer stage WST, as shown in FIG. 21.

At the moment when the switching process (linkage) of the encoder usedfor the position control of wafer stage WST within the XY plane is to beperformed, encoders Enc1, Enc2, Enc3 and Enc4 are positioned abovescales 39Y₁, 39Y₂, 39X₁, and 39X₂, respectively, as shown in FIG. 21.When having a look at FIG. 21, it looks as though the encoder is goingto be switched from encoder Enc1 to encoder Enc4, however, as is obviousfrom the fact that the measurement direction is different in encoderEnc1 and encoder Enc4, it does not have any meaning even if themeasurement values (count values) of encoder Enc1 are given without anychanges as the initial value of the measurement values of encoder Enc4.

Therefore, in the embodiment, main controller 20 switches frommeasurement/servo by the three encoders Enc1, Enc2 and Enc3 tomeasurement/servo by the three encoders Enc2, Enc3 and Enc4. Morespecifically, as it can be seen from FIG. 21, this method is differentfrom the concept of a normal encoder linkage, and in this method thelinkage is made not from one head to another head, but from acombination of three heads (an encoder) to a combination of anotherthree heads (an encoder). Incidentally, in the three heads and anotherthree heads, the different head is not limited to one. Further, in FIG.21, encoder Enc3 was switched to encoder Enc4, however, instead ofencoder Enc4, for example, the encoder can be switched, for example, tothe encoder adjacent to encoder Enc3.

First of all, main controller 20 solves the simultaneous equations (23a)to (23c) based on the measurement values C₁, C₂, and C₃ of encodersEnc1, Enc2, and Enc3, and computes positional information (X, Y, θz) ofwafer stage WST within the XY plane.

Next, main controller 20 substitutes X and θz computed above into theaffine transformation of the next formula (24), and determines theinitial value of the measurement values of encoder (X head) Enc4.

C4=X+p ₄*cos θz−q ₄*sin θz  (24)

In formula (24) above, p₄ and q₄ are the X-coordinate value and theY-coordinate value of encoder Enc4. As Y coordinate value q₄ of encoderEnc4, the positional information of the irradiation point of themeasurement beam which was acquired on calibration of the head positionpreviously described is read from memory 34 and is used, while asX-coordinate value p₄ of encoder Enc4, the design position informationof the irradiation point of the measurement beam is read from memory 34and is used.

By giving initial value C₄ as an initial value of encoder Enc4, linkagewill be completed without any contradiction, having maintained theposition (X, Y, θz) of wafer stage WST in directions of three degree offreedom. From then onward, the following simultaneous equations (23b) to(23d) are solved, using the measurement values C₂, C₃, and C₄ ofencoders Enc2, Enc3, and Enc4 which are used after the switching, and aposition coordinate (X, Y, θz) of wafer stage WST is computed.

C ₂=−(p ₂ −X)sin θz+(q ₂ −Y)cos θz  (23b)

C ₃=(p ₃ −X)cos θz+(q ₃ −Y)sin θz  (23c)

C ₄=(p ₄ −X)cos θz+(q ₄ −Y)sin θz  (23d)

Incidentally, in the case the fourth encoder is a Y head, instead ofusing theoretical formula (23d), a simultaneous equation (23b) (23c)(23e), which uses the following theoretical formula (23e) can be used.

C ₄=−(p ₄ −X)sin θz+(q ₄ −Y)cos θz  (23e)

However, because measurement value C₄ computed above is a measurementvalue of a corrected encoder whose measurement errors of the variousencoders previously described have been corrected, main controller 20performs inverse correction on measurement value C₄ and computes a rawvalue C₄′ which is the value before correction, and determines raw valueC₄′ as the initial value of the measurement value of encoder Enc4, usingthe stage position induced error correction information, the scaleinduced error correction information (e.g., the degree of flatness ofthe grating surface (flatness), and/or the correction information of thegrating pitch of the scale (and the correction information of thegrating deformation) and the like), the Abbe offset quantity (the Abbeerror correction information) and the like previously described.

In this case, the inverse correction refers to the processing ofcomputing measurement value C₄′ based on measurement value C₄, under thehypothesis that C₄ is a measurement value of the encoder aftercorrection when count value C₄′ of the encoder on which no correctionhas been performed is corrected using the stage position induced errorcorrection information previously described, the scale origin errorcorrection information described above, and Abbe offset quantity (Abbeerror correction information).

Now, the position control interval (control sampling interval) of waferstage WST, as an example, is 96 [μsec], however, the measurementinterval (measurement sampling interval) of an interferometer or anencoder has to be at a much higher-speed. The reason why the sampling ofthe interferometer and the encoder has to be performed at a higher-speedthan the control sampling is because both the interferometer and theencoder count the intensity change (fringe) of the interference light,and when the sampling becomes rough, measurement becomes difficult.

However, with the position servo control system of wafer stage WST, thesystem updates the current position of wafer stage WST at every controlsampling interval of 96 [μsec], performs calculation to set the positionto a target position, and outputs thrust command values and the like.Accordingly, the positional information of the wafer stage is necessaryat every control sampling interval of 96 [μsec], and the positionalinformation in between the sampling intervals will not be necessary inthe position control of wafer stage WST. The interferometer and theencoder merely perforin sampling at a high speed so as not to lose trackof the fringe. Therefore, in the embodiment, at all times while waferstage WST is located in the effective stroke range previously described,main controller 20 continues to receive the measurement values (countvalues) from each encoder (a head) of the encoder system, regardless ofwhether or not the the encoder watches the scale. And, main controller20 performs the switching operation (linkage operation between theplurality of encoders) previously described, in synchronization with thetiming of the position control of the wafer stage performed every 96[μsec]. In such an arrangement, the switching operation of anelectrically high-speed encoder will not be required, which means thatcostly hardware to realize such a high-speed switching operation doesnot necessarily have to be arranged. FIG. 22 conceptually shows thetiming of position control of wafer stage WST, the uptake of the countvalues of the encoder, and the switching of the encoder, which areperformed in the embodiment. In FIG. 22, reference code CSCK shows ageneration timing of a sampling clock of the position control of waferstage WST, and reference code MSCK shows a generation timing of ameasurement sampling clock of the encoder (and the interferometer).Further, reference code CH typically shows the switching (linkage) ofthe encoder.

Now, in the description above, the switching that could be performedfrom one combination of heads (encoders) to another combination of heads(encoders), and the timing when the switching can be performed are to beknown, however, they also must be known in the actual sequence as well.It is also preferable to prepare the scheduling of the timing to carryout the linkage in advance.

Therefore, in the embodiment, main controller 20 prepares the schedulefor the switching (the switching from one combination of three heads (e.g., Enc1, Enc2, and Enc3) to another combination of three heads (e. g.,Enc4, Enc2, and Enc3), and the timing of the switch) of the threeencoders (heads) which are used for measuring the positional informationof wafer stage WST in directions of three degrees of freedom (X, Y, θz)within the XY plane, based on the movement course (target track) ofwafer stage WST, and stores the scheduling result in the storage unitsuch as memory 34.

In this case, if a retry (redoing) is not considered, the contents ofthe schedule in every shot map (an exposure map) becomes constant,however, in actual practice, because a retry must be considered, it ispreferable for main controller 20 to constantly update the scheduleslightly ahead while performing the exposure operation.

Incidentally, in the embodiment above, because the description was maderelated to the principle of the switching method of the encoder used forposition control of wafer stage WST, expressions such as encoder (head)Enc1, Enc2, Enc3, and Enc4 were used, however, it goes without sayingthat head Enc1 and Enc2 indicate either Y head 64 of head units 62A and62C or a pair of Y heads 64 y ₁ and 64 y ₂, representatively, and headsEnc3 and Enc4 indicates X head 66 of head unit 62B and 62D,representatively. Further, for similar reasons, in FIGS. 20A, 20B and21, the placement of encoders (heads) Enc1, Enc2, Enc3 and the like isshown differently from the actual placement (FIG. 3 and the like).

<<Generalization of Switching and Linkage Principle>>

In the embodiment, in order to measure the position coordinates of waferstage WST in directions of three degree of freedom (X, Y, θz), among theX encoders (heads) and Y encoders (heads) that constitute encodersystems 70A to 70D, at least three heads which at least include one Xhead and at least two Y heads are constantly used. Therefore, when thehead which is to be used is switched along with the movement of waferstage WST, a method of switching from a combination of three heads toanother combination of three heads is employed, so as to continuouslylink the measurement results of the stage position before and after theswitching. This method will be referred to as a first method.

However, when considering the basic principle of the switching andlinkage process from a different point of view, it can also be viewed asa method of switching one head of the three heads that are used toanother head. This method will be referred to as a second method. Now,the second method will be described, referring to a switching andlinkage process from Y head 64 _(C3) to 64 _(C4) as an example,indicated by an arrow e₁ in FIG. 7A.

The basic procedure of the switching process is, while both a first head64 ₀₃ which will be suspended later and a second head 64 ₀₄ which willbe newly used face the corresponding scale 39Y₂, main controller 20executes the restoration of the second head 64 _(C4) and the setting ofthe measurement values (linkage process), and the switching (andsuspension of the first head 64C₃) of the head monitoring themeasurement value.

When the measurement value is set (linkage process), main controller 20predicts a measurement value C_(Y4) of the second head 64 _(C4) using ameasurement value C_(Y3) of the first head 64 _(C3). In this case,according to theoretical formula (22b), measurement values C_(Y3) andC_(Y4) of Y heads 64 _(C3) and 64 _(C4) follow formulas (25a) and (25b)below.

C _(Y3)=−(p ₃ −X)sin θz+(q ₃ −Y)cos θz  (25a)

C _(Y4)=−(p ₄ −X)sin θz+(q ₄ −Y)cos θz  (25b)

In this case, (p₃, q₃) and (p_(a), q₄) are the X and Y setting positions(or to be more precise, the X and Y positions of the measurement points)of Y heads 64 _(C3) and 64 _(C4). To make it more simple, suppose thatthe Y setting positions of Y heads 64 _(C3) and 64 _(C4) are equal(q₃=q₄). Under this assumption, from formulas (25a) and (25b) above, thefollowing formula (26) is obtained.

C _(Y4) =C _(Y3)+(p ₃ −p ₄)sin θz  (26)

Accordingly, by substituting the measurement value of first head 64_(C3) which will be suspended later into C_(Y3) on the right-hand sideof formula (26) above and obtaining C_(Ya) on the left-hand side, themeasurement value of the second head 64 ₀₄ which will be newly used canbe predicted.

Predicted value C_(Ya) that has been obtained is to be set as theinitial value of the measurement value of the second head 64 _(C4) at aproper timing. After the setting, the first head 64 _(C3) is suspendedwhen it moves off scale 39Y₂, which completes the switching and linkageprocess.

Incidentally, when the measurement value of the second head 64 _(C4) ispredicted using formula (26) above, a value of rotation angle θz, whichis obtained from the measurement results of another head that is active,should be substituted into variable θz. In this case, another head thatis active is not limited to the first head 64 _(C3) which is subject toswitching, but includes all the heads that provide the measurementresults necessary to obtain rotation angle θz. In this case, because thefirst head 64 _(C3) is a head of head unit 62C, rotation angle θz can beobtained using the first head 64 _(C3), and for example, one of theheads of head unit 62A that faces Y scale 39Y₁ during the switching. Or,a value of rotation angle θz, which can be obtained from the measurementresults of X interferometer 126 of interferometer system 118, Yinterferometer 16, or Z interferometer 43A and 43B and the like can besubstituted into variable θz.

Incidentally, the switching and linkage process between Y heads wasexplained as an example here, however, the switching and linkage processbetween X heads, and further, also the switching and linkage processbetween two heads belonging to different head units such as between theX head and the Y head can also be explained similarly as the secondmethod.

Therefore when the principle of the linkage process is generalized, themeasurement value of another head newly used is predicted so that theresults of the position measurement of wafer stage WST is linkedcontinuously before and after the switching, and the predicted value isset as the initial value of the measurement values of the second head.In this case, in order to predict the measurement values of anotherhead, theoretical formulas (22a) and (22b) and the measurement values ofthe active heads including the head which will be suspended latersubject to the switching will be used as required. However, for therotation angle in the θz direction of wafer stage WST which is necessaryon the linkage, a value which is obtained from the measurement resultsof interferometer system 118 can be used.

As is described above, even if it is premised that at least three headsare constantly used to measure the position of wafer age WST indirections of three degree of freedom (X, Y, θz) as in the precedingfirst method, if focusing on only the two heads which are direct objectsof the switching and linkage process without referring to the concreteprocedure of predicting the measurement value of another head newlyused, the observation on the second method where one head out of thethree heads used is switched to another head can be realized.

Incidentally, the description so far was made on the premise that theposition of wafer stage WST in directions of three degrees of freedom(X, Y, θz) was measured using at least three heads. However, even in thecase of measuring the position of two or more in directions of m degreesof freedom (the choice of the degrees of freedom is arbitrary) using atleast m heads, it is obvious that the observation of the second methodwhere one head out of m heads used is switched to another head can berealized, as in the description above.

Next, a description will be made in which under a specific condition, anobservation of a method (to be referred to as a third method) where acombination of two heads is switched to a combination of another twoheads can be consistently realized.

In the example above, switching and linkage process between both heads64 _(C3) and 64 _(C4) is executed, while Y heads 64 _(C3) and 64 _(C4)each face the corresponding Y scale 39Y₂. During this operation,according to the placement of the scale and the head employed inexposure apparatus 100 of the embodiment, one Y head (expressed as 64_(A)) of head unit 62A faces Y scale 39Y₁ and measures relativedisplacement of Y scale 39Y₁ in the Y-axis direction. Therefore, aswitching and linkage process will be considered from a firstcombination of Y heads 64 _(C3) and 64 _(A) to a second combination of Yheads 64 _(C4) and 64 _(A).

A measurement value C_(Ya) of Y head 64 _(A) follows formula (25c)below, according to theoretical formula (22b).

C _(YA)=−(p _(A) −X)sin θz+(q _(A) −Y)cos θz  (25c)

In this case, (p_(A), q_(A)) is the X and Y setting position (or to bemore precise, the X and Y positions of the measurement point) of Y head64 _(A). To make it more simple, suppose that Y setting position q_(A)of Y head 64 _(A) is equal to Y setting positions q₃ and q₄ of Y heads64 _(C3) and 64 _(C4) (q_(A)=q₃=q₄).

When theoretical formulas (25a) and (25c), which measurement valuesC_(Y3) and C_(Ya) of Y heads 64 _(C3) and 64 _(A) of the firstcombination follow, are substituted into theoretical formula (25b),which measurement value C_(Y3) of Y head 64 _(C4) that is newly usedfollows, formula (27) below is derived.

C _(Y4)=(1−c)C _(Y3) −c*C _(YA)  (27)

However, constant c=(p₃−p₄)/(q_(A)−q₃). Accordingly, by substituting themeasurement values of Y heads 64 _(C3) and 64 _(A) into C_(Y3) andC_(YA) on the right-hand side of formula (27) above and obtaining C_(Y4)on the left-hand side, the measurement value of Y head 64 _(C4) newlyused can be predicted.

Predicted value C_(Y4) that has been obtained is to be set as theinitial value of the measurement value of Y head 64 _(C4) at a propertiming. After the setting, Y head 64 _(C3) is suspended when it movesoff scale 39Y₂, which completes the switching and linkage process.

Incidentally, according to the placement of the scale and the heademployed in exposure apparatus 100 of the embodiment, at least one Xhead 66 faces X scale 39X₁ or 39X₂ and measures the relativedisplacement in the X-axis direction. Then, according to the measurementresults of the three heads, which are one X head 66 two Y heads 64 _(C3)and 64 _(A), the position of wafer stage WST in directions of threedegrees of freedom (X, Y, θz) is computed. However, in the example ofthe switching and linkage process described above, X head 66 merelyplays the role of a spectator, and the observation of the third methodwhere a combination of two heads, Y heads 64 _(C3) and 64 _(A) isswitched to a combination of another two heads, Y head 64 _(C4) and 64_(A), is consistently realized.

Accordingly, under the premise that the use of three heads isindispensable to measure the position of wafer stage WST in directionsof three degrees of freedom (X, Y, θz), the first method was proposed asa general method of the switching and linkage process that could beapplied to every case, regardless of the placement of the scale and thehead employed in exposure apparatus 100 of the embodiment. And, based onthe concrete placement of the scale and the head employed in exposureapparatus 100 of the embodiment and the concrete procedure of thelinkage process, the observation of the third method could be realizedunder a particular condition.

Incidentally, in addition to the first method, in the switching andlinkage process of the encoder head by the second and third methodsdescribed above, the measurement value of another head to be newly usedwas predicted so that the position coordinate of wafer stage WST whichis monitored is continuously linked before and after the switching, andthis predicted value was set as an initial value for the measurementvalue of another head. Instead of the processing above, the measurementerror of another head including the measurement error generated by theswitching and linkage process can be computed and the correction datacan be made. And, while the another head is being used, the correctiondata that has been made can be used for servo drive control of waferstage WST. In this case, based on the correction data, positionalinformation of wafer stage WST measured by the another head can becorrected, or a target position of wafer stage WST for servo control canbe corrected. Furthermore, in the exposure operation, servo drivecontrol of the reticle stage is performed, following the movement ofwafer stage WST. Therefore, based on the correction data, instead ofcorrecting the servo control of wafer stage WST, the follow-up servocontrol of the reticle stage can be corrected. Further, according tothese control system, the measurement value of the head before theswitching may be set as an initial value of another head without anychanges. Incidentally, when making the correction data, not only theencoder system but also other measurement systems that the exposureapparatus in the embodiment has, such as the interferometer systems,should be appropriately used.

Next, a parallel processing operation that uses wafer stage WST andmeasurement stage MST in exposure apparatus 100 of the embodiment willbe described, based on FIGS. 23 to 36. Incidentally, during theoperation below, main controller 20 performs the open/close control ofeach valve of liquid supply unit 5 of local liquid immersion unit 8 andliquid recovery unit 6 in the manner previously described, and water isconstantly filled in the space right under tip lens 191 of projectionoptical system PL. However, in the description below, for the sake ofsimplicity, the explanation related to the control of liquid supply unit5 and liquid recovery unit 6 will be omitted. Further, many drawings areused in the operation description hereinafter, however, reference codesmay or may not be given to the same member for each drawing. Morespecifically, the reference codes written are different for eachdrawing, however, such members have the same configuration, regardlessof the indication of the reference codes. The same can be said for eachdrawing used in the description so far.

FIG. 23 shows a state where exposure by the step-and-scan method isbeing performed on wafer W (in this case, as an example, the wafer is awafer midway of a certain lot (one lot contains 25 or 50 wafers)) onwafer stage WST. In this state, measurement stage MST can wait at awithdrawal position where it avoids bumping into wafer stage WST,however, in the embodiment, measurement stage MST is moving, followingwafer stage WST while keeping a predetermined distance. Therefore, whenmeasurement stage MST moves into a contact state (or a proximity state)with wafer stage WST after the exposure has been completed, the samedistance as the predetermined distance referred to above will be enoughto cover the movement distance.

During this exposure, main controller 20 controls the position(including the θz rotation) of wafer table WTB (wafer stage WST) withinthe XY plane, based on the measurement values of at least three encodersout of two X heads 66 (X encoders 70B and 70D) shown surrounded by acircle in FIG. 23 facing X scales 39X₁ and 39X₂, respectively, and two Yheads 64 (Y encoders 70A and 70C) shown surrounded by a circle in FIG.23 facing Y scales 39Y₁ and 39Y₂, respectively, the pitching amount orrolling amount, and yawing amount of wafer stage WST measured byinterferometer system 118, the stage position induced error correctioninformation (correction information obtained by formula (10) or formula(11) previously described) of each encoder corresponding to the Zposition, the correction information of the grating pitch of each scaleand correction information of the warp of the grid line, and the Abbeoffset quantity (Abbe error correction information). Further, maincontroller 20 controls the position of wafer table WTB in the Z-axisdirection, the θy rotation (rolling), and the θx rotation (pitching),based on measurement values of one pair each of Z sensors 74 _(1,j) and74 _(2,j), and 76 _(1,q) and 76 _(2,q) that face one end and the otherend (in the embodiment, Y scales 39Y₁ and 39Y₂) of the wafer table WTBsurface in the X-axis direction. Incidentally, the position of wafertable WTB in the Z-axis direction and the θy rotation (rolling) can becontrolled based on the measurement value of Z sensors 74 _(1,j), 74_(2,j), 76 _(1,q), and 76 _(2,q), and the θx rotation (pitching) can becontrolled based on the measurement values of Y interferometer 16. Inany case, the control (focus leveling control of wafer W) of theposition of wafer table WTB in the Z-axis direction, the θy rotation,and the θx rotation during this exposure is performed, based on resultsof a focus mapping performed in advance by the multipoint AF systempreviously described.

Main controller 20 performs the exposure operation described above,based on results of wafer alignment (e g Enhanced Global Alignment(EGA)) that has been performed beforehand and on the latest baseline andthe like of alignment systems AL1, and AL2₁ to AL2₄, by repeating amovement operation between shots in which wafer stage WST is moved to ascanning starting position (an acceleration starting position) forexposure of each shot area on wafer W, and a scanning exposure operationin which a pattern formed on reticle R is transferred onto each shotarea by a scanning exposure method. Incidentally, the exposure operationdescribed above is performed in a state where water is retained in thespace between tip lens 191 and wafer W. Further, exposure is performedin the order from the shot area located on the −Y side to the shot arealocated on the +Y side in FIG. 23. Incidentally, details on the EGAmethod are disclosed, for example, in U.S. Pat. No. 4,780,617description and the like.

And before the last shot area on wafer W is exposed, main controller 20controls stage drive system 124 based on the measurement value of Yinterferometer 18 while maintaining the measurement value of Xinterferometer 130 to a constant value, and moves measurement stage MST(measurement table MTB) to the position shown in FIG. 24. When themeasurement stage is moved, the edge surface of CD bar 46 (measurementtable MTB) on the −Y side touches the edge surface of wafer table WTB onthe +Y side. Incidentally, measurement table MTB and wafer table WTB canbe separated, for example, at around 300 μm in the Y-axis directionwhile monitoring, for example, the interferometer that measures theposition of each table in the Y-axis direction or the measurement valuesof the encoder so as to maintain a non-contact state (proximity state).After wafer stage WST and measurement stage MST are set to thepositional relation shown in FIG. 24 during the exposure of wafer W,both stages are moved while maintaining this positional relation.

Subsequently, as shown in FIG. 25, main controller 20 begins theoperation of driving measurement stage MST in the −Y-direction, and alsobegins the operation of driving wafer stage WST toward unloadingposition UP, while maintaining the positional relation of wafer tableWTB and measurement table MTB in the Y-axis direction. When theoperations begin, in the embodiment, measurement stage MST is moved onlyin the −Y direction, and wafer stage WST is moved in the −Y directionand the −X direction.

When main controller 20 simultaneously drives wafer stage WST andmeasurement stage MST in the manner described above, the water (water ofliquid immersion area 14 shown in FIG. 25) which was retained in thespace between tip lens 191 of projection unit PU and wafer Wsequentially moves over wafer W→plate 28→CD bar 46→measurement tableMTB, along with the movement of wafer stage WST and measurement stageMST to the −Y side. Incidentally, during the movement above, wafer tableWTB and measurement table MTB maintain the contact state (or proximitystate) previously described. Incidentally, FIG. 25 shows a state justbefore the water of liquid immersion area 14 is moved over to CD bar 46from plate 28. Further, in the state shown in FIG. 25, main controller20 controls the position (including the θz rotation) of wafer table WTB(wafer stage WST) within the XY plane, based on the measurement values(and the stage position induced error correction information, thecorrection information of the grating pitch of the scale and thecorrection information of the grid line of encoders 70A, 70B or 70Dstored in memory 34, corresponding to the pitching amount, rollingamount, yawing amount, and the Z position of wafer stage WST measured byinterferometer system 118) of the three encoders 70A, 70B, and 70D.

When wafer stage WST and measurement stage MST are drivensimultaneously, slightly in the directions above furthermore from thestate shown in FIG. 25, respectively, because the position measurementof wafer stage WST (wafer table WTB) by Y encoder 70A (and, 70C) will nolonger be possible, main controller 20 switches the control of the Yposition and the θz rotation of wafer stage WST (wafer table WTB) justbefore this, from a control based on the measurement values of Yencoders 70A and 70C to a control based on the measurement values of Yinterferometer 16 and Z interferometers 43A and 43B. Then, after apredetermined time later, measurement stage MST reaches a position wherebaseline measurement (hereinafter appropriately referred to as Sec-BCHK(interval)) of the secondary alignment system is performed at apredetermined interval (in this case, at each wafer exchange) as shownin FIG. 26. Then, main controller 20 stops measurement stage MST at theposition, and drives wafer stage WST furthermore toward unloadingposition UP and then stops wafer stage WST at unloading position UP,while measuring the X position of wafer stage WST using X head 66 (Xlinear encoder 70B) shown in FIG. 26 surrounded by a circle that faces Xscale 39X₁ and also measuring the position in the Y-axis direction andthe θz rotation measure using Y interferometer 16 and Z interferometers43A and 43B. Incidentally, in the state shown in FIG. 26, the water isretained in the space between measurement table MTB and tip lens 191.

Subsequently, as shown in FIGS. 26 and 27, main controller 20 adjuststhe θz rotation of CD bar 46, based on the measurement values of Y-axislinear encoders 70E and 70F configured by Y heads 64 y ₁ and 64 y ₂shown in FIG. 27 surrounded by a circle that face a pair of referencegrids 52 on CD bar 46 supported by measurement stage MST, respectively,and also adjusts the XY position of CD bar 46, based on the measurementvalue of primary alignment system AL1 which detects reference mark Mlocated on or in the vicinity of center line CL of measurement tableMTB. Then, in this state, main controller 20 performs the Sec-BCHK(interval) in which the baseline (the relative position of the foursecondary alignment systems with respect to primary alignment systemAL1) of the four secondary alignment systems AL2₁ to AL2₄ is obtained bysimultaneously measuring reference mark M on CD bar 46 located withinthe field each secondary alignment system, respectively, using the foursecondary alignment systems AL2₁ to AL2₄. In parallel with this Sec-BCHK(an interval), main controller 20 gives a command to a drive system ofan unload arm (not shown) so that wafer W on wafer stage WST suspendedat unload position UP is unloaded, and also drives wafer stage WST inthe +X direction so that the stage is moved to loading position LP,while keeping a vertical movement pin CT (not shown in FIG. 26, refer toFIG. 27) elevated by a predetermined amount, which was driven upward onthe unloading.

Next, as shown in FIG. 28, main controller 20 moves measurement stageMST to an optimal waiting position (hereinafter referred to as “optimalscrum waiting position”), which is the optimal waiting position formoving measurement stage MST from the state distanced from wafer stageWST into the contact state (or proximity state) previously describedwith wafer stage WST. In parallel with this, main controller 20 gives acommand to a drive system of a load arm (not shown) so that a new waferW is loaded on wafer table WTB. In this case, because vertical movementpin CT is maintaining the state of being elevated by a predeterminedamount, wafer loading can be performed in a short period of time whencompared with the case when vertical movement pin CT is driven downwardand is housed inside the wafer holder. Incidentally, FIG. 28 shows astate where wafer W is loaded on wafer table WTB.

In the embodiment, the optimal scrum waiting position of measurementstage MST referred to above is appropriately set according to theY-coordinate of alignment marks arranged on the alignment shot area onthe wafer. Further, in the embodiment, the optimal scrum waitingposition is decided so that wafer stage WST can move into the contactstate (or proximity state) at the position where wafer stage WST stopsfor wafer alignment.

During this exposure, main controller 20 switches the control ofposition of wafer table WTB within the XY plane, from the controlpreviously described based on measurement values of encoder 70B for theX-axis direction, Y interferometer 16 and Z interferometers 43A and 43Bfor the Y-axis direction and the θz rotation, to a control based on themeasurement values of at least three encoders out of two X heads 66 (Xencoders 70B and 70D) shown surrounded by a circle in FIG. 29 facing Xscales 39X₁ and 39X₂, respectively, and two Y heads 64 y ₂ and 64 y ₁ (Yencoders 70A and 70C) shown surrounded by a circle in FIG. 29 facing Yscales 39Y₁ and 39Y₂, respectively, the pitching amount or rollingamount, and yawing amount of wafer stage WST measured by interferometersystem 118, the stage position induced error correction information(correction information obtained by formula (10) or formula (11)previously described) of each encoder corresponding to the Z position,the correction information of the grating pitch of each scale andcorrection information of the warp of the grid line, and the Abbe offsetquantity (Abbe error correction information).

Then, main controller 20 performs the frothier process of Pri-BCHK inwhich fiducial mark FM is detected using primary alignment system AL1.At this point in time, measurement stage MST is waiting at the optimalscrum waiting position described above.

Next, while controlling the position of wafer stage WST based on themeasurement values of at least the three encoders and each correctioninformation described above, main controller 20 begins the movement ofwafer stage WST in the +Y direction toward a position where thealignment marks arranged in three first alignment shot areas aredetected.

Then, when wafer stage WST reaches the position shown in FIG. 30, maincontroller 20 stops wafer stage WST. Prior to this, main controller 20activates (turns on) Z sensors 72 a to 72 d at the point when Z sensors72 a to 72 d begins to move over wafer table WTB or at the point before,and measures the Z position and the inclination (θy rotation and θxrotation) of wafer table WTB.

After wafer stage WST is stopped as in the description above, maincontroller 20 detects the alignment marks arranged in the three firstalignment shot areas substantially at the same time and alsoindividually (refer to the star-shaped marks in FIG. 30), using primaryalignment system AL1, and secondary alignment systems AL2₂ and AL2₃, andmakes a link between the detection results of the three alignmentsystems AL1, AL2₂, and AL2₃ and the measurement values (measurementvalues after the correction according to each correction information) ofat least the three encoders above at the time of the detection, andstores them in the internal memory.

As in the description above, in the embodiment, the shift to the contactstate (or proximity state) between measurement stage MST and wafer stageWST is completed at the position where detection of the alignment marksof the first alignment shot areas is performed, and from this position,main controller 20 begins to move both stages WST and MST in the +Ydirection (step movement toward the position for detecting alignmentmarks arranged in five second alignment shot areas) in the contact state(or proximity state). Prior to starting the movement of both stages WSTand MST in the +Y direction, as shown in FIG. 30, main controller 20begins irradiation of a detection beam from irradiation system 90 of themultipoint AF system (90 a, 90 b) toward wafer table WTB. Accordingly, adetection area of the multipoint AF system is formed on wafer table WTB.

Then, when both stages WST and MST reach the position shown in FIG. 31during the movement of both stages WST and MST in the +Y direction, maincontroller 20 performs the former process of the focus calibration, andobtains the relation between the measurement values (surface positioninformation on one side and the other side of wafer table WTB in theX-axis direction) of Z sensors 72 a, 72 b, 72 c, and 72 d, in a statewhere a straight line (center line) in the Y-axis direction passingthrough the center (substantially coinciding with the center of wafer W)of wafer table WTB coincides with straight line LV previously described,and the detection results (surface position information) of a detectionpoint (the detection point located in or around the center, among aplurality of detection points) on the surface of measurement plate 30 ofthe multipoint AF system (90 a, 90 b). At this point, liquid immersionarea 14 is located in the vicinity of the border of CD bar 46 and wafertable WTB. More specifically, liquid immersion area 14 is in a statejust before it is passed over to wafer table WTB from CD bar 46.

Then, when both stages WST and MST move further in the +Y directionwhile maintaining the contact state (or proximity state), and reach theposition shown in FIG. 32, the alignment marks arranged in the fivesecond alignment shot areas are detected substantially at the same timeas well as individually (refer to the star-shaped marks in FIG. 31),using the five alignment systems AL1, and AL2₁ to AL2₄ and a link ismade between the detection results of the five alignment systems AL1,and AL2₁ to AL2₄ and the measurement values (measurement values afterthe correction according to each correction information) of the threeencoders 70A, 70C, and 70D at the time of the detection, and stored inthe internal memory. At this point in time, since the X head that facesX scale 39X₁ and is located on straight line LV does not exist, maincontroller 20 controls the position within the XY plane of wafer tableWTB based on the measurement values of X head 66 facing X scale 39X₂ (Xlinear encoder 70D) and Y linear encoders 70A and 70C.

As is described above, in the embodiment, the positional information(two-dimensional positional information) of a total of eight alignmentmarks can be detected at the point when the detection of the alignmentmarks in the second alignment shot areas is completed. Therefore, atthis stage, main controller 20 can perform a statistical computationsuch as the one disclosed in, for example, Kokai (Japanese UnexaminedPatent Application Publication) No. 61-44429 bulletin (the correspondingU.S. Pat. No. 4,780,617 description) and the like, to obtain the scaling(shot magnification) of wafer W, and can adjust the optical propertiesof projection optical system PL, such as for example, the projectionmagnification, by controlling an adjustment 68 (refer to FIG. 6) basedon the shot magnification which has been computed. Adjustment unit 68adjusts the optical properties of projection optical system PL, forexample, by driving a particular movable lens that configures projectionoptical system PL, or changing gas pressure in an airtight chamberformed between particular lenses that configure projection opticalsystem PL or the like.

Further, after the simultaneous detection of the alignment marksarranged in the five second alignment shot areas is completed, maincontroller 20 starts again movement in the +Y direction of both stagesWST and MST in the contact state (or proximity state), and at the sametime, starts the focus mapping using Z sensors 72 a to 72 d and themultipoint AF system (90 a, 90 b), as is shown in FIG. 32.

Then, when both stages WST and MST reach the position with whichmeasurement plate 30 is located directly below projection optical systemPL shown in FIG. 33, main controller 20 performs the Pri-BCHK latterprocess and the focus calibration latter process. In this case, thePri-BCHK latter process refers to a processing in which a projectedimage (aerial image) of a pair of measurement marks on reticle Rprojected by projection optical system PL is measured, using aerialimage measurement unit 45 previously described which has aerial imagemeasurement slit pattern SL formed on measurement plate 30, and themeasurement results (aerial image intensity depending on the XY positionof wafer table WTB) are stored in the internal memory. In thisprocessing, the projected image of the pair of measurement marks ismeasured in an aerial image measurement operation by the slit scanmethod, using a pair of aerial image measurement slit patterns SL,similar to the method disclosed in, U.S. Patent Application PublicationNo. 2002/0041377 description and the like. Further, the focuscalibration latter process refers to a processing in which maincontroller 20 measures the aerial image of a measurement mark formed ona mark plate (not shown) on reticle R or on reticle stage RST usingaerial image measurement unit 45, while controlling the position (Zposition) of measurement plate 30 (wafer table WTB) related to theoptical axis direction of projection optical system PL, based on thesurface position information of wafer table WTB (wafer stage WST)measured by Z sensors 72 a, 72 b, 72 c, and 72 d, and then measures thebest focus position of projection optical system PL based on themeasurement results, as shown in FIG. 33. For example, the measurementoperation of the projected image of the measurement mark is disclosedin, for example, the pamphlet of International Publication No. WO05/124834 and the like. While moving measurement plate 30 in the Z-axisdirection, main controller 20 takes in the measurement values of Zsensors 74 _(1,4),74 _(2,4), 76 _(1,3), and 76 _(2,3) in synchronizationwith taking in the output signal from aerial image measurement unit 45.Then, main controller 20 stores the values of Z sensors 74 _(1,4),74_(2,4), 76 _(1,3), and 76 _(2,3) corresponding to the best focusposition of projection optical system PL in a memory (not shown).Incidentally, the reason why the position (Z position) related to theoptical axis direction of projection optical system PL of measurementplate 30 (wafer stage WST) is controlled using the surface positioninformation measured in the focus calibration latter process by Zsensors 72 a, 72 b, 72 c, and 72 d is because the focus calibrationlatter process is performed during the focus mapping previouslydescribed.

In this case, because liquid immersion area 14 is formed betweenprojection optical system PL and measurement plate 30 (wafer table WTB),the measurement of the aerial image is performed via projection opticalsystem PL and the water. Further, because measurement plate 30 and thelike is installed in wafer stage WST (wafer table WTB), and the lightreceiving element and the like is installed in measurement stage MST,the measurement of the aerial image is performed while maintaining thecontact state (or proximity state) of wafer stage WST and measurementstage MST, as shown in FIG. 33. By the measurement described above,measurement values (more specifically, surface position information ofwafer table WTB) of Z sensors 74 _(1,4), 74 _(2,4), 76 _(1,3), and 76_(2,3) corresponding to the best focus position of projection opticalsystem PL are obtained, in a state where the straight line (the centerline) in the Y-axis direction passing through the center of wafer tableWTB coincides with straight line LV previously described.

Then, main controller 20 computes the baseline of primary alignmentsystem AL1, based on the results of the Pri-BCHK former process and theresults of the Pri-BCHK latter process described above. With this, basedon the relation between the measurement values (surface positioninformation of wafer table WTB) of Z sensors 72 a, 72 b, 72 c, and 72 dobtained in the focus calibration former process described above and thedetection results (surface position information) of the detection pointon the surface of measurement plate 30 of the multipoint AF system (90a, 90 b), and the measurement values (more specifically, surfaceposition information of wafer table WTB) of Z sensors 74 _(1,4), 74_(2,4), 76 _(1,3), and 76 _(2,3) corresponding to the best focusposition of projection optical system PL which are obtained in the focuscalibration latter process described above, main controller 20 obtainsthe offset at a representative detection point (the detection pointlocated in or around the center, among a plurality of detection points)of the multipoint AF system (90 a, 90 b) with respect to the best focusposition of projection optical system PL and adjusts the detectionorigin of the multipoint AF system, for example, by an optical method sothat the offset becomes zero.

In this case, from the viewpoint of improving throughput, only oneprocessing of the Pri-BCHK latter process described above and the focuscalibration latter process can be performed, or the procedure can moveon to the next processing without performing both processing. As amatter of course, in the case the Pri-BCHK latter process is notperformed, the Pri-BCHK former process described earlier also does nothave to be performed, and in this case, main controller 20 only has tomove wafer stage WST from loading position LP to a position where thealignment marks arranged in the first alignment shot areas are detected.Incidentally, in the case Pri-BCHK process is not performed, thebaseline which is measured by a similar operation just before theexposure of a wafer exposed earlier than wafer W subject to exposure isused. Further, when the focus calibration latter process is notperformed, similar to the baseline, the best focus position ofprojection optical system PL which is measured just before the exposureof a preceding wafer is used.

Incidentally, in the state shown in FIG. 33, the focus mappingpreviously described is being continued.

When wafer stage WST reaches the position shown in FIG. 34 after apredetermined time by movement in the +Y direction of both stages WSTand MST in the contact state (or proximity state) described above, maincontroller 20 stops wafer stage WST at that position, while also makingmeasurement stage MST continue the movement in the +Y direction. Then,main controller 20 almost simultaneously and individually detects thealignment marks arranged in the five third alignment shot areas (referto star-shaped marks in FIG. 34) using five alignment systems AL1 andAL2₁ to AL2₄, links the detection results of five alignment systems AL1and AL2₁ to AL2₄ and the measurement values of at least three encoders(measurement values after correction by the correction information) outof the four encoders at the time of the detection and stores them in theinternal memory. At this point in time, the focus mapping is beingcontinued.

Meanwhile, after a predetermined period of time from the suspension ofwafer stage WST described above, measurement stage MST and wafer stageWST moves from the contact state (or proximity state) into a separationstate. After moving into the separation state, main controller 20 stopsthe movement of measurement stage MST when measurement stage MST reachesan exposure start waiting position where measurement stage MST waitsuntil exposure is started.

Next, main controller 20 starts to move wafer stage WST in the +Ydirection toward a position where alignment marks arranged in threefourth alignment shot areas are detected. At this point in time, thefocus mapping is being continued. Meanwhile, measurement stage WST iswaiting at the exposure start waiting position described above.

Then, when wafer stage WST reaches the position shown in FIG. 35, maincontroller 20 immediately stops wafer stage WST, and almostsimultaneously and individually detects the alignment marks arranged inthe three fourth alignment shot areas on wafer W (refer to star-shapedmarks in FIG. 35) using primary alignment system AL1 and secondaryalignment systems AL2₂ and AL2₃, links the detection results of threealignment systems AL1, AL2₂ and AL2₃ and the measurement values of atleast three encoders (measurement values after correction by thecorrection information) out of the four encoders at the time of thedetection, and stores them in the internal memory. Also at this point intime, the focus mapping is being continued, and measurement stage MST isstill waiting at the exposure start waiting position. Then, using thedetection results of a total of 16 alignment marks and the measurementvalues (measurement values after the correction by each correctioninformation) of the corresponding encoders obtained in the mannerdescribed above, main controller 20 computes array information(coordinate values) of all the shot areas on wafer W on a coordinatesystem (for example, an XY coordinate system whose origin is placed atthe center of wafer table WTB) that is set by the measurement axes ofthe four encoders, using the EGA method disclosed in, for example, U.S.Pat. No. 4,780,617 description and the like.

Next, main controller 20 continues the focus mapping while moving waferstage WST in the +Y direction again. Then, when the detection beam fromthe multipoint AF system (90 a, 90 b) begins to miss the wafer Wsurface, as is shown in FIG. 36, main controller 20 ends the focusmapping. After that, based on the results of the wafer alignment (EGA)described earlier performed in advance, and the measurement results ofthe latest baselines of the five alignment systems AL1 and AL2₁ to AL2₄,and the like, main controller 20 performs exposure by the step-and-scanmethod in a liquid immersion exposure and sequentially transfers areticle pattern to a plurality of shot areas on wafer W. Afterwards,similar operations are repeatedly performed so as to expose theremaining wafers within the lot.

As is described in detail above, according to exposure apparatus 100related to the embodiment, in the case of moving wafer stage WST in apredetermined direction, such as, for example, the Y-axis direction atthe time of wafer alignment time or exposure, wafer stage WST is drivenin the Y-axis direction, based on the measurement information of theencoder system, the positional information (including inclinationinformation, e. g., rotation information in the θx direction) of waferstage WST in a direction different from the Y-axis direction, thecharacteristic information (e. g., the degree of flatness of the gratingsurface, and/or a grating formation error) of the scale, and the Abbeoffset quantity of the scale. More specifically, wafer stage WST isdriven to compensate for the measurement errors of the encoder system(encoders 70A and 70C) caused by the displacement (including theinclination) of wafer stage WST in a direction different from the Y-axisdirection and the scale. In the embodiment, main controller 20 driveswafer stage WST in the Y-axis direction, based on the measurement valuesof encoders 70A and 70C that measure positional information of waferstage WST in a predetermined direction, such as the Y-axis direction,the stage position induced error correction information (the correctioninformation which is computed by formula (10) previously described) thatcorresponds to the positional information of wafer stage WST in adirection different (a direction besides the measurement direction) fromthe Y-axis direction at the time of measurement, the correctioninformation (the correction information which takes into considerationthe unevenness (degree of flatness) of the Y scale) of the grating pitchof the Y scale, the correction information of the warp of grid line 38of the Y scale, and the correction information of the Abbe offsetquantity of the Y scale. In the manner described above, stage drivesystem 124 is controlled based on the measurement values of encoders 70Aand 70C which are corrected according to each correction information ofthe relative displacement of scales 39Y₁ and 39Y₂ and Y head 64 in thenon-measurement direction, the grating pitch of Y scales 39Y₁ and 39Y₂and the warp of grid line 38, and the measurement error of encoders 70Aand 70C due to the Abbe error due to the Abbe offset quantity of the Yscale, and wafer stage WST is driven in the Y-axis direction. In thiscase, the count values of encoders 70A and 70C are the same results aswhen an ideal grating (diffraction grating) is measured with an idealencoder (head). An ideal grating (diffraction grating), here, refers toa grating whose surface of the grating a completely flat surfaceparallel to the movement plane (the XY plane) of the stage, and thepitch direction of the grating is parallel to the beam of theinterferometer and the distance between the grid lines is completelyequal. An ideal encoder (head) refers to a head whose optical axis isperpendicular to the movement plane of the stage and whose count valuesdo not change by Z displacement, leveling, yawing and the like.

Further, in the case wafer stage WST is moved in the X-axis direction,wafer stage WST is driven in the X-axis direction, based on themeasurement information of the encoder system, the positionalinformation (including inclination information, e. g., rotationinformation in the θy direction) of wafer stage WST in a directiondifferent from the X-axis direction, the characteristic information (e.g., the degree of flatness of the grating surface, and/or a gratingformation error) of the scale, and the Abbe offset quantity of the Xscale. More specifically, wafer stage WST is driven to compensate forthe measurement errors of the encoder system (encoders 70B and 70D)caused by the displacement (including the inclination) of wafer stageWST in a direction different from the X-axis direction. In theembodiment, main controller 20 drives wafer stage WST in the X-axisdirection, based on the measurement values of encoders 70B and 70D whichmeasure the positional information of wafer stage WST in the X-axisdirection, the positional information of wafer stage WST in a directiondifferent from the X-axis direction at the time of the measurement(non-measurement direction), such as, for example, the stage positioninduced error correction information (the correction information whichis computed by formula (11) previously described) that corresponds tothe positional information of wafer stage WST in the θy direction, θzdirection, and the Z-axis direction measured by Z interferometers 43Aand 43B of interferometer system 118, the correction information (thecorrection information which takes into consideration the unevenness(degree of flatness) of the X scales) of the grating pitch of the Xscales, the correction information of the warp of grid line 37 of the Xscales, and the correction information of the Abbe error due to the Abbeoffset quantity of X scales 39X₁ and 39X₂. In the manner describedabove, stage drive system 124 is controlled based on the measurementvalues of encoders 70B and 70D which are corrected according to eachcorrection information of the relative displacement of scales 39X₁ and39X₂ and X head 66 in the non-measurement direction, the grating pitchof X scales 39X₁ and 39X₂ and the warp of grid line 37, and themeasurement error of encoders 70B and 70D due to the Abbe error due tothe Abbe offset quantity of X scales 39X₁ and 39X₂, and wafer stage WSTis driven in the X-axis direction. In this case, the count values ofencoders 70B and 70D are the same results as when an ideal grating(diffraction grating) is measured with an ideal encoder (head).

Accordingly, it becomes possible to drive wafer stage WST using anencoder in a desired direction with good precision, without beingaffected by the relative motion in directions other than the direction(measurement direction) of the head and the scale to be measured,without being affected by the Abbe error, without being affected by theunevenness of the scale, and without being affected by the grating pitchof the scale and the grating warp.

Further, according to exposure apparatus 100 related to the embodiment,for example, while the lot is being processed, main controller 20measures the positional information (including the θz rotation) of waferstage WST within the XY plane (the movement plane) by three heads(encoders), which at least include one each of an X head (X encoder) anda Y head (Y encoder) of the encoder system. Then, based on themeasurement results of the positional information and the positionalinformation ((X, Y) coordinate value) in the movement plane of the threeheads used for measuring the positional information, main controller 20drives wafer stage WST within the XY plane. In this case, maincontroller 20 drives wafer stage WST within the XY plane, whilecomputing the positional information of wafer stage WST within the XYplane using the affine transformation relation. Accordingly, it becomespossible to control the movement of wafer stage WST with good precisionwhile switching the head (encoder) used for control during the movementof wafer stage WST, using the encoder system including head units 62A to62D which respectively have a plurality of Y heads 64 or a plurality ofX heads 66.

Further, according to exposure apparatus 100 related to the embodiment,prior to starting the lot processing in which wafer stage WST is driven,such as, for example, during the start-up of the apparatus, as one of aseries of calibration of the encoder system that measures the positionalinformation of wafer stage WST in the XY plane, a calibration process toacquire the Abbe offset quantity of each scale (grating) previouslydescribed is performed. More specifically, for each scale of the encodersystem, main controller 20 inclines wafer stage WST at an angle α withrespect to an XY plane in the periodic direction of the grating based onthe measurement values of interferometer system 118 which measures theangle of inclination of wafer stage WST to the XY plane in the periodicdirection of the grating, and then based on the measurement values ofthe encoder system before and after the inclination and information ofangle α measured by interferometer system 118, main controller 20computes the Abbe offset quantity of the grating surface. Then, maincontroller 20 stores the information that has been computed in memory34.

And, on the drive of wafer stage WST described above, while computingthe Abbe error using the Abbe offset quantity of the surface of eachscale (grating) stored in memory 34 and the information of the angle ofinclination of the wafer stage measured by interferometer system 118,main controller 20 corrects the measurement values of the encoder systemusing the Abbe error as correction information of the Abbe error.

Further, according to exposure apparatus 100 of the embodiment, forrelative movement between illumination light IL irradiated on wafer Wvia reticle R, projection optical system PL, and water Lq fromillumination system 10 and wafer W, main controller 20 drives waferstage WST on which wafer W is placed with good precision, based on themeasurement values of each encoder described above, the stage positioninduced error correction information of each encoder corresponding tothe positional information of the wafer stage in the non-measurementdirection at the time of the measurement, the correction information ofthe grating pitch of each scale and the correction information of thegrid line, and the correction information of the Abbe error.

Accordingly, by scanning exposure and liquid immersion exposure, itbecomes possible to form a desired pattern of reticle R in each shotarea on the wafer with good precision.

Further, in the embodiment, as it has been described earlier based onFIGS. 29 and 30, prior to the measurement (EGA alignment measurement) ofthe alignment marks arranged in the three first alignment shot areas onwafer W by alignment systems AL1, AL2₂, and AL2₃, main controller 20switches the measurement unit used for the position control of waferstage WST from interferometer system 118 to the encoder system (switchesthe control of the position of wafer table WTB within the XY plane fromthe irregular control previously described to the control based on themeasurement values of at least three encoders out of encoders 70B and70D and encoders 70A and 70C). According to this, even if there are someerrors in the measurement values of the X position and the Y position ofwafer stage WST by the encoder system just after the switching, there isan advantage of the errors being consequently canceled by the EGAperformed next.

Further, according to the embodiment, on acquiring the stage positioninduced error correction information of the measurement values of theencoder previously described, main controller 20 changes wafer stage WSTinto a plurality of different attitudes, and for each attitude, in astate where the attitude of wafer stage WST is maintained based on themeasurement results of interferometer system 118, moves wafer stage WSTin the Z-axis direction in a predetermined stroke range whileirradiating a detection light from head 64 or 66 of the encoder on thespecific area of scales 39Y₁, 39Y₂, 39X₁ or 39X₂, and samples themeasurement results of the encoder during the movement. According tothis, change information (for example, an error characteristics curve asshown in the graph in FIG. 12) of the measurement values of the encodercorresponding to the position in the direction (Z-axis direction)orthogonal to the movement plane of wafer stage WST for each attitudecan be obtained.

Then, by performing a predetermined operation based on this samplingresult, namely the change information of the measurement values of theencoder corresponding to the position of wafer stage WST in the Z-axisdirection for each attitude, main controller 20 obtains the correctioninformation of the measurement values of the encoder corresponding tothe positional information of wafer stage WST in the non-measurementdirection. Accordingly, the stage position induced error correctioninformation for correcting the measurement errors of the encoder due toa relative change between the head and the scale in the non-measurementdirection can be determined by a simple method.

Further, in the embodiment, in the case of deciding the correctioninformation above, for a plurality of heads that configure the same headunit, such as, for example, a plurality of Y heads 64 that configurehead unit 62A, a detection light is irradiated from each Y head 64 onthe same specific area of the corresponding Y scale 39Y₁ and a samplingis performed on the measurement results of the encoder described above,and because the correction information of each encoder configured byeach Y head 64 and Y scale 39Y₁ is decided based on the sampling result,by using this correction information, a geometric error which occursbecause of the gradient of the head can also be consequently corrected.In other words, when main controller 20 obtains by the correctioninformation with the plurality of encoders corresponding to the samescale as the object, it obtains the correction information of theencoder serving as the object taking into consideration the geometricerror which occurs by the gradient of the head of the object encoderwhen wafer stage WST is moved in the Z-axis direction. Accordingly, inthe embodiment, a cosine error caused by different gradient angles in aplurality of heads is also not generated. Further, even if a gradientdoes not occur in Y head 64, for example, when a measurement erroroccurs in an encoder caused by the optical properties (telecentricity)of the head or the like, obtaining the correction information similarlycan prevent the measurement error from occurring, which in turn preventsthe deterioration of the position control precision of wafer stage WST.That is, in the embodiment, wafer stage WST is driven so as tocompensate for the measurement errors (hereinafter also referred to as ahead induced error) of the encoder system which occur due to the headunit. Incidentally, for example, correction information of themeasurement values of the encoder system can be computed, based on thecharacteristic information (for example, including the slant of the headand/or the optical properties and the like) of the head unit.

Incidentally, in the embodiment above, the measurement values of theencoder system were corrected based on the correction informationpreviously described so as to compensate for the measurement error dueto the Abbe error, however, the present invention is not limited tothis, and, for example, the target position to which wafer stage WST isto be positioned can be corrected based on the correction information,while driving wafer stage WST based on the measurement values of theencoder system. Or, especially in the exposure operation, the positionof reticle stage RST can be corrected based on the correctioninformation previously described, while, for example, driving waferstage WST based on the measurement values of the encoder system.

Further, the measuring method of Abbe offset quantity described in theembodiment above is a mere example. For example, because the Z sensormeasures the Z position of the grating surface of the scale, measurementplate 30 used for the focus measurement of projection optical system PLwhose surface is substantially flush with the upper surface of waferstage WST can also be detected with the grating surface of the scaleusing the Z sensor, and based on this detection result, the Abbe offsetquantity can be obtained.

Incidentally, in the embodiment above, an invention related to theswitching of the head of the encoder and the linkage of the measurementvalue, an invention related to the correction of various measurementerrors (e. g., stage position induced error, head induced error, scaleinduced error, Abbe error and the like) of the encoder system, aninvention (invention about the reset of the encoder system) in which theposition control of the wafer stage using the encoder system was startedonce more after every wafer exchange, an invention related to theswitching timing in which the switching operation of the encoder (head)is executed at a timing in synchronization with the position control ofthe wafer stage, an invention to prepare the schedule for the switchingtiming based on the movement course of the wafer stage and the like werecarried out by the same exposure apparatus. However, these inventionscan be executed alone or in any combination.

Further, a correction of the stage position induced error, the headinduced error, the scale induced error and the Abbe error previouslydescribed or a combination of two or more of the corrections can also beperformed.

Incidentally, in each of the embodiments above, in order to simplify thedescription, main controller 20 had control over each part of theexposure apparatus such as the stage system, the interferometer system,the encoder system and the like, however, the present invention is notlimited to this, and it is a matter of course that at least a part ofthe control performed by main controller 20 can be shared with aplurality of controllers. For example, a stage controller, whichcontrols wafer stage WST based on the measurement values of the encodersystem, the Z sensor and the interferometer system, can be arranged tooperate under main controller 20. Further, the control that maincontroller 20 performs does not necessarily have to be realized byhardware, and the control can be realized by software using a computerprogram that sets the operation of main controller 20 or each operationof some controllers that share the control as previously described.

Incidentally, the configuration and the placement of the encoder system,the interferometer system, the multipoint AF system, the Z sensor andthe like in the embodiment above is an example among many, and it is amatter of course that the present invention is not limited to this. Forexample, in the embodiment above, an example was indicated of a casewhere the pair of Y scales 39Y₁ and 39Y₂ used for the measurement of theposition in the Y-axis direction and the pair of X scales 39X₁ and 39X₂used for the measurement of the position in the X-axis direction arearranged on wafer table WTB, and corresponding to the scales, the pairof head units 62A and 62C is placed on one side and the other side ofthe X-axis direction of projection optical system PL, and the pair ofhead units 62B and 62D is placed on one side and the other side of theY-axis direction of projection optical system PL. However, the presentinvention is not limited to this, and of Y scales 39Y₁ and 39Y₂ used forthe measurement of the position in the Y-axis direction and X scales39X₁ and 39X₂ used for the measurement of the position in the X-axisdirection, at least one of the scales can be arranged singularly onwafer table WTB, without being a pair, or, of the pair of head units 62Aand 62C and the pair of head units 62B and 62D, at least one of the headunits can be arranged, singularly. Further, the extension direction ofthe scale and the extension direction of the head unit are not limitedto an orthogonal direction such as the X-axis direction and the Y-axisdirection in the embodiment above, and it can be any direction as longas the directions intersect each other. Further, the periodic directionof the diffraction grating can be a direction orthogonal to (orintersecting with) the longitudinal direction of each scale, and in sucha case, a plurality of heads of the corresponding head unit should beplaced in a direction orthogonal to the periodic direction of thediffraction grating. Further, each head unit can have a plurality ofheads placed without any gap in a direction orthogonal to the periodicdirection of the diffraction grating.

Further, in the embodiment above, the case has been described where thegrating section (the X scale and the Y scale) was placed on a surface ofwafer stage WST parallel to the XY plane, or to be more specific, on theupper surface, however, the present invention is not limited to this,and the grating section can be placed as a matter of course on the lowersurface, as well as the side surface, or a head can be arranged on themovable body side such as the wafer stage, and the a grating (atwo-dimensional grating or a one-dimensional grating placedtwo-dimensionally) can be placed external to the movable body. In thiscase, when a Z sensor is also placed on the upper surface of the movablebody, the grating externally placed can also be used as a reflectionsurface that reflects the measurement beam from the Z sensor.

Incidentally, in the embodiment above, rotation information (pitchingamount) of wafer stage WST in the θx direction was measured byinterferometer system 118, however, for example, the pitching amount canbe obtained from the measurement values of either of the pair of Zsensors 74 _(i,j) or 76 _(p,q). Or, similar to head units 62A and 62C,for example, one Z sensor or a pair of Z sensors can be arranged inproximity each head of head units 62B and 62D, and the pitching amountcan be obtained from X scales 39X₁ and 39X₂ and the measurement value ofthe Z sensors that face the scales, respectively. Accordingly, itbecomes possible to measure the positional information of wafer stageWST in directions of six degrees of freedom, or more specifically, theX-axis, Y-axis, Z-axis, θx, θy, and θz directions using the encoder andthe Z sensor previously described, without using interferometer system118. The measurement of the positional information of wafer stage WST indirections of six degrees of freedom using the encoder and the Z sensorpreviously described can be performed not only in the exposure operationbut also in the alignment operation and/or the focus mapping operationpreviously described.

Further, in the embodiment above, wafer stage WST was driven based onthe measurement value of the encoder system, for example, in the case ofexposure, however, for example, an encoder system the measures theposition of reticle stage RST can be added, and reticle stage RST can bedriven based on the correction information that corresponds to themeasurement values of the encoder system and the positional informationof the reticle stage in the non-measurement direction measured byreticle interferometer 116.

Further, in the embodiment above, the case has been described where theapparatus is equipped with one fixed primary alignment system and fourmovable secondary alignment systems, and alignment marks arranged in the16 alignment shot areas on the wafer are detected by the sequenceaccording to the five alignment systems. However, the secondaryalignment system does not need to be movable, and, further, the numberof the secondary alignment systems does not matter. The important thingis that there is at least one alignment system that can detect thealignment marks on the wafer.

Incidentally, in the embodiment above, the exposure apparatus which isequipped with measurement stage MST separately from wafer stage WST wasdescribed as in the exposure apparatus disclosed in the pamphlet ofInternational Publication No. WO 2005/074014, however, the presentinvention is not limited to this, and for example, as is disclosed in,for example, Kokai (Japanese Patent Unexamined Application Publication)No. 10-214783 bulletin and the corresponding U.S. Pat. No. 6,341,007description, and in the pamphlet of International Publication No. WO98/40,791 and the corresponding U.S. Pat. No. 6,262,796 description andthe like, even in an exposure apparatus by the twin wafer stage methodthat can execute the exposure operation and the measurement operation(e. g., mark detection by the alignment system) almost in parallel usingtwo wafer stages, it is possible to perform the position control of eachwafer stage the encoder system (refer to FIG. 3 and the like) previouslydescribed. By appropriately setting the placement and length of eachhead unit not only during the exposure operation but also during themeasurement operation, the position control of each wafer stage can beperformed continuing the use of the encoder system previously described,however, a head unit that can be used during the measurement operationcan be arranged, separately from head units (62A to 62D) previouslydescribed. For example, four head units can be placed in the shape of across with one or two alignment systems in the center, and during themeasurement operation above, the positional information of each waferstage WST can be measured using these head units and the correspondingscales. In the exposure apparatus by the twin wafer stage method, atleast two scales each is arranged in the two wafer stages, respectively,and when the exposure operation of the wafer mounted on one of the waferstages is completed, in exchange with the stage, the other wafer stageon which the next wafer that has undergone mark detection and the likeat the measurement position is mounted is placed at the exposureposition. Further, the measurement operation performed in parallel withthe exposure operation is not limited to the mark detection of wafersand the like by the alignment system, and instead of this, or incombination with this, the surface information (step information) of thewafer can also be detected.

Incidentally, in the embodiment above, the case has been described whereSec-BCHK (interval) is performed using CD bar 46 on the measurementstage MST side while each wafer is exchanged on the wafer stage WSTside, however, the present invention is not limited to this, and atleast one of an illuminance irregularity measurement (and illuminancemeasurement), aerial image measurement, wavefront aberration measurementand the like can be performed using a measuring instrument (measurementmember) of measurement stage MST, and the measurement results can bereflected in the exposure of the wafer performed later on. To be moreconcrete, for example, projection optical system PL can be adjusted byadjustment unit 68 based on the measurement results.

Further, in the embodiment above, a scale can also be placed onmeasurement stage MST, the position control of the measurement stage canbe performed using the encoder system (head unit) previously described.More specifically, the movable body that performs the measurement ofpositional information using the encoder system is not limited to thewafer stage.

Incidentally, when reducing the size and weight of wafer stage WST istaken into consideration, it is desirable to place the scale as close aspossible to wafer W on wafer stage WST, however, when the size of thewafer stage is allowed to increase, by increasing the size of the waferstage and increasing the distance between the pair of scales that isplaced facing the stage, positional information of at least two each inthe X-axis and Y-axis directions, that is, a total of four positionalinformation, can be measured constantly during the exposure operation.Further, instead of increasing the size of the wafer stage, for example,a part of the scale can be arranged so that it protrudes from the waferstage, or, by placing the scale on the outer side of wafer stage mainbody using an auxiliary plate on which at least one scale is arranged,the distance between the pair of scales that face the stage can beincreased as in the description above.

Further, in the embodiment above, in order to prevent deterioration inthe measurement accuracy caused by adhesion of a foreign material,contamination, and the like to Y scales 39Y₁ and 39Y₂, and X scales 39X₁and 39X₂, for example, a coating can be applied on the surface so as tocover at least the diffraction grating, or a cover glass can bearranged. In this case, especially in the case of a liquid immersiontype exposure apparatus, a liquid repellent protection film can becoated on the scale (a grating surface), or a liquid repellent film canbe formed on the surface (upper surface) of the cover glass.Furthermore, the diffraction grating was formed continually onsubstantially the entire area in the longitudinal direction of eachscale, however, for example, the diffraction grating can be formedintermittently divided into a plurality of areas, or each scale can beconfigured by a plurality of scales. Further, in the embodiment above,an example was given in the case where an encoder by the diffractioninterference method is used as the encoder, however, the presentinvention is not limited to this, and a method such as the so-calledpickup method and the like can be used, and the so-called scan encoderswhose details are disclosed in, for example, U.S. Pat. No. 6,639,686description and the like, can also be used.

Further, in the embodiment above, as the Z sensor, instead of the sensorby the optical pick-up method referred to above, for example, a sensorconfigured by a first sensor (the sensor can be a sensor by the opticalpick-up method or other optical displacement sensors) that projects aprobe beam on a measurement object surface and optically reads thedisplacement of the measurement object surface in the Z-axis directionby receiving the reflected light, a drive section that drives the firstsensor in the Z-axis direction, and a second sensor (e. g. encoders andthe like) that measures the displacement of the first sensor in theZ-axis direction can be used. In the Z sensor having the configurationdescribed above, a mode (the first servo control mode) in which thedrive section drives the first sensor in the Z-axis direction based onthe output of the first sensor so that the distance between themeasurement object surface, such as the surface of the scale and thefirst sensor in the Z-axis direction is always constant, and a mode (thefirst servo control mode) in which a target value of the second sensoris given from an external section (controller) and the drive sectionmaintains the position of the first sensor in the Z-axis direction sothat the measurement values of the second sensor coincides with thetarget value can be set. In the case of the first servo control mode, asthe output of the Z sensor, the output of the measuring section (thesecond sensor) can be used, and in the case of the second servo controlmode, the output of the second sensor can be used. Further, in the caseof using such a Z sensor, and an encoder is employed as the secondsensor, as a consequence, the positional information of wafer stage WST(wafer table WTB) in directions of six degrees of freedom can bemeasured using an encoder. Further, in the embodiment above, as the Zsensor, a sensor by other detection methods can be employed.

Further, in the embodiment above, the configuration of the plurality ofinterferometers used for measuring the positional information of waferstage WST and their combination are not limited to the configuration andthe combination previously described. The important thing is that aslong as the positional information of wafer stage WST of the directionexcept for the measurement direction of the encoder system can bemeasured, the configuration of the interferometers and their combinationdoes not especially matter. The important thing is that there should bea measurement unit (it does not matter whether it is an interferometeror not) besides the encoder system described above that can measure thepositional information of wafer stage WST in the direction except forthe measurement direction of the encoder system. For example, the Zsensor previously described can be used as such measurement unit.

Further, in the embodiment above, the Z sensor was arranged besides themultipoint AF system, however, for example, in the case the surfaceposition information of the shot area subject to exposure of wafer W canbe detected with the multipoint AF system on exposure, then the Z sensordoes not necessarily have to be arranged.

Incidentally, in the embodiment above, pure water (water) was used asthe liquid, however, it is a matter of course that the present inventionis not limited to this. As the liquid, a liquid that is chemicallystable that has high transmittance to illumination light IL and safe touse, such as a fluorine-containing inert liquid may be used. As thefluorine-containing inert liquid, for example, Fluorinert (the brandname of 3M United States) can be used. The fluorine-containing inertliquid is also excellent from the point of cooling effect. Further, asthe liquid, liquid which has a refractive index higher than pure water(a refractive index is around 1.44), for example, liquid having arefractive index equal to or higher than 1.5 can be used. As this typeof liquid, for example, a predetermined liquid having C—H binding or O—Hbinding such as isopropanol having a refractive index of about 1.50,glycerol (glycerin) having a refractive index of about 1.61, apredetermined liquid (organic solvent) such as hexane, heptane ordecane, or decalin (decahydronaphthalene) having a refractive index ofabout 1.60, or the like can be cited. Alternatively, a liquid obtainedby mixing arbitrary two or more of these liquids may be used, or aliquid obtained by adding (mixing) the predetermined liquid to (with)pure water can be used. Alternatively, as the liquid, a liquid obtainedby adding (mixing) base or acid such as H⁺, Cs⁺, K⁺, Cl⁻, SO₄ ²⁻, or PO₄²⁻ to (with) pure water can be used. Moreover, a liquid obtained byadding (mixing) particles of Al oxide or the like to (with) pure watercan be used. These liquids can transmit ArF excimer laser light.Further, as the liquid, liquid, which has a small absorption coefficientof light, is less temperature-dependent, and is stable to a projectionoptical system (tip optical member) and/or a photosensitive agent (or aprotection film (top coat film), an antireflection film, or the like)coated on the surface of a wafer, is preferable. Further, in the case anF₂ laser is used as the light source, fomblin oil can be selected.

Further, in the embodiment above, the recovered liquid may be reused,and in this case, a filter that removes impurities from the recoveredliquid is preferably arranged in a liquid recovery unit, a recovery pipeor the like.

Further, in the embodiment above, the case has been described where theexposure apparatus is a liquid immersion type exposure apparatus,however, the present invention is not limited to this, and it can alsobe applied to a dry type exposure apparatus that performs exposure ofwafer W without liquid (water).

Further, in the embodiment above, the case has been described where thepresent invention is applied to a scanning exposure apparatus by astep-and-scan method or the like. However, the present invention is notlimited to this, but may also be applied to a static exposure apparatussuch as a stepper. Even with the stepper or the like, by measuring theposition of a stage on which an object subject to exposure is mounted byencoders, generation of position measurement error caused by airfluctuations can substantially be nulled likewise. Furthermore, evenwith the stepper, it becomes possible to set the position of the stagewith high precision based on the measurement values of the encoder andeach correction information previously described, and as a consequence,it becomes possible to transfer a reticle pattern onto an object withhigh precision. Further, the present invention can also be applied to areduction projection exposure apparatus by a step-and-stitch method thatsynthesizes a shot area and a shot area, an exposure apparatus by aproximity method, a mirror projection aligner, or the like.

Further, the magnification of the projection optical system in theexposure apparatus of the embodiment above is not only a reductionsystem, but also may be either an equal magnifying system or amagnifying system, and projection optical system PL is not only adioptric system, but also may be either a catoptric system or acatadioptric system, and in addition, the projected image may be eitheran inverted image or an upright image. Moreover, the exposure area towhich illumination light IL is irradiated via projection optical systemPL is an on-axis area that includes optical axis AX within the field ofprojection optical system PL. However, for example, as is disclosed inthe pamphlet of International Publication No. WO 2004/107011, theexposure area can also be an off-axis area that does not include opticalaxis AX, similar to a so-called inline type catadioptric system, in partof which an optical system (catoptric system or catadioptric system)that has plural reflection surfaces and forms an intermediate image atleast once is arranged, and which has a single optical axis. Further,the illumination area and exposure area described above are to have arectangular shape. However, the shape is not limited to rectangular, andcan also be circular arc, trapezoidal, parallelogram or the like.

Further, the light source of the exposure apparatus in the embodimentabove is not limited to the ArF excimer laser, and a pulsed laser lightsource such as a KrF excimer laser (output wavelength 248 nm), an F₂laser (output wavelength 157 nm), an Ar₂ laser (output wavelength 126nm), or a Kr₂ laser (output wavelength 146 nm), or an ultrahigh-pressure mercury lamp that generates a bright line such as theg-line (wavelength 436 nm) or the i-line (wavelength 365 nm) can also beused as the light source. Further, a harmonic wave generating unit of aYAG laser or the like can also be used. Besides the sources above, as isdisclosed in, for example, the pamphlet of International Publication No.WO 1999/46835 (the corresponding U.S. Pat. No. 7,023,610 description), aharmonic wave, which is obtained by amplifying a single-wavelength laserbeam in the infrared or visible range emitted by a DFB semiconductorlaser or fiber laser as vacuum ultraviolet light, with a fiber amplifierdoped with, for example, erbium (or both erbium and ytteribium), and byconverting the wavelength into ultraviolet light using a nonlinearoptical crystal, can also be used.

Further, in the embodiment above, illumination light IL of the exposureapparatus is not limited to the light having a wavelength equal to ormore than 100 nm, and it is needless to say that the light having awavelength less than 100 nm can be used. For example, in recent years,in order to expose a pattern equal to or less than 70 nm, development ofan EUV exposure apparatus that makes an SOR or a plasma laser as a lightsource generate an EUV (Extreme Ultraviolet) light in a soft X-ray range(e.g. a wavelength range from 5 to 15 nm), and uses a total reflectionreduction optical system designed under the exposure wavelength (e.g.13.5 nm) and the reflective mask is underway. In the EUV exposureapparatus, the arrangement in which scanning exposure is performed bysynchronously scanning a mask and a wafer using a circular arcillumination can be considered, and therefore, the present invention canalso be suitably applied to such an exposure apparatus. Besides such anapparatus, the present invention can also be applied to an exposureapparatus that uses charged particle beams such as an electron beam oran ion beam.

Further, in the embodiment above, a transmissive type mask (reticle) isused, which is a transmissive substrate on which a predetermined lightshielding pattern (or a phase pattern or a light attenuation pattern) isformed. Instead of this reticle, however, as is disclosed in, forexample, U.S. Pat. No. 6,778,257 description, an electron mask (which isalso called a variable shaped mask, an active mask or an imagegenerator, and includes, for example, a DMD (Digital Micromirror Device)that is a type of a non-emission type image display device (spatiallight modulator) or the like) on which a light-transmitting pattern, areflection pattern, or an emission pattern is formed according toelectronic data of the pattern that is to be exposed can also be used.In the case of using such a variable shaped mask, because the stage onwhich a wafer or a glass plate is mounted moves relatively with respectto the variable shaped mask, by driving the stage based on themeasurement values of an encoder and each correction informationpreviously described while measuring the position of the stage withinthe movement plane using the encoder system and performing the linkageoperation between a plurality of encoders previously described, anequivalent effect as the embodiment described above can be obtained.

Further, as is disclosed in, for example, the pamphlet of InternationalPublication No. WO 2001/035168, the present invention can also beapplied to an exposure apparatus (lithography system) that formsline-and-space patterns on a wafer by forming interference fringes onthe wafer.

Moreover, the present invention can also be applied to an exposureapparatus that synthesizes two reticle patterns via a projection opticalsystem and almost simultaneously performs double exposure of one shotarea by one scanning exposure, as is disclosed in, for example, Kohyo(published Japanese translation of International Publication for PatentApplication) No. 2004-519850 bulletin (the corresponding U.S. Pat. No.6,611,316 description).

Further, an apparatus that forms a pattern on an object is not limitedto the exposure apparatus (lithography system) described above, and forexample, the present invention can also be applied to an apparatus thatforms a pattern on an object by an ink jet method.

Incidentally, an object on which a pattern is to be formed (an objectsubject to exposure to which an energy beam is irradiated) in theembodiment above is not limited to a wafer, and can be other objectssuch as a glass plate, a ceramic substrate, a film member, or a maskblank.

The use of the exposure apparatus is not limited only to the exposureapparatus for manufacturing semiconductor devices, but the presentinvention can also be widely applied to an exposure apparatus fortransferring a liquid crystal display device pattern onto a rectangularglass plate and an exposure apparatus for producing organic ELs,thin-film magnetic heads, imaging devices (such as CCDs), micromachines,DNA chips, and the like. Further, the present invention can be appliednot only to an exposure apparatus for producing microdevices such assemiconductor devices, but can also be applied to an exposure apparatusthat transfers a circuit pattern onto a glass plate or silicon wafer toproduce a mask or reticle used in a light exposure apparatus, an EUVexposure apparatus, an X-ray exposure apparatus, an electron-beamexposure apparatus, and the like.

Incidentally, the movable body drive system and the movable body drivemethod of the present invention can be applied not only to the exposureapparatus, but can also be applied widely to other substrate processingapparatuses (such as a laser repair apparatus, a substrate inspectionapparatus and the like), or to apparatuses equipped with a movable bodysuch as a stage that moves within a two-dimensional plane such as aposition setting apparatus for specimen or a wire bonding apparatus inother precision machines.

Further, the exposure apparatus (the pattern forming apparatus) of theembodiment above is manufactured by assembling various subsystems, whichinclude the respective constituents that are recited in the claims ofthe present application, so as to keep predetermined mechanicalaccuracy, electrical accuracy and optical accuracy. In order to securethese various kinds of accuracy, before and after the assembly,adjustment to achieve the optical accuracy for various optical systems,adjustment to achieve the mechanical accuracy for various mechanicalsystems, and adjustment to achieve the electrical accuracy for variouselectric systems are performed. A process of assembling varioussubsystems into the exposure apparatus includes mechanical connection,wiring connection of electric circuits, piping connection of pressurecircuits, and the like among various types of subsystems. Needless tosay, an assembly process of individual subsystem is performed before theprocess of assembling the various subsystems into the exposureapparatus. When the process of assembling the various subsystems intothe exposure apparatus is completed, a total adjustment is performed andvarious kinds of accuracy as the entire exposure apparatus are secured.Incidentally, the making of the exposure apparatus is preferablyperformed in a clean room where the temperature, the degree ofcleanliness and the like are controlled.

Incidentally, the disclosures of the various publications, the pamphletsof the International Publications, and the U.S. Patent ApplicationPublication descriptions and the U.S. Patent descriptions that are citedin the embodiment above and related to exposure apparatuses and the likeare each incorporated herein by reference.

Next, an embodiment of a device manufacturing method in which theexposure apparatus (pattern forming apparatus) described above is usedin a lithography process will be described.

FIG. 37 shows a flowchart of an example when manufacturing a device (asemiconductor chip such as an IC or an LSI, a liquid crystal panel, aCCD, a thin film magnetic head, a micromachine, and the like). As shownin FIG. 37, first of all, in step 201 (design step), function andperformance design of device (such as circuit design of semiconductordevice) is performed, and pattern design to realize the function isperformed. Then, in step 202 (a mask making step), a mask (reticle) ismade on which the circuit pattern that has been designed is formed.Meanwhile, in step 203 (a wafer fabrication step), wafers aremanufactured using materials such as silicon.

Next, in step 204 (wafer processing step), the actual circuit and thelike are formed on the wafer by lithography or the like in a manner thatwill be described later, using the mask and the wafer prepared in steps201 to 203. Then, in step 205 (device assembly step), device assembly isperformed using the wafer processed in step 204. Step 205 includesprocesses such as the dicing process, the bonding process, and thepackaging process (chip encapsulation), and the like when necessary.

Finally, in step 206 (an inspecting step), the operation check test of adevice made by step 205, the durability test are checked. After theseprocesses, the devices are completed and are shipped out.

FIG. 38 is a flowchart showing a detailed example of step 204 describedabove. Referring to FIG. 38, in step 211 (oxidation step), the surfaceof wafer is oxidized. In step 212 (CDV step), an insulating film isformed on the wafer surface. In step 213 (an electrode formation step),an electrode is formed on the wafer by deposition. In step 214 (an ionimplantation step), ions are implanted into the wafer. Each of the abovesteps 211 to step 214 constitutes the preprocess in each step of waferprocessing, and the necessary processing is chosen and is executed ateach stage.

When the above-described preprocess ends in each stage of waferprocessing, post-process is executed as follows. First of all, in thepost-process, first in step 215 (a resist formation step), aphotosensitive agent is coated on the wafer. Then, in step 216 (exposurestep), the circuit pattern of the mask is transferred onto the wafer bythe exposure apparatus (pattern forming apparatus) described above andthe exposure method (pattern forming method) thereof. Next, in step 217(development step), the wafer that has been exposed is developed, and instep 218 (etching step), an exposed member of an area other than thearea where resist remains is removed by etching. Then, in step 219(resist removing step), when etching is completed, the resist that is nolonger necessary is removed.

By repeatedly performing the pre-process and the post-process, multiplecircuit patterns are formed on the wafer.

By using the device manufacturing method of the embodiment describedabove, because the exposure apparatus (pattern forming apparatus) in theembodiment above and the exposure method (pattern forming method)thereof are used in the exposure step (step 216), exposure with highthroughput can be performed while maintaining the high overlay accuracy.Accordingly, the productivity of highly integrated microdevices on whichfine patterns are formed can be improved.

While the above-described embodiments of the present invention are thepresently preferred embodiments thereof, those skilled in the art oflithography systems will readily recognize that numerous additions,modifications, and substitutions may be made to the above-describedembodiments without departing from the spirit and scope thereof. It isintended that all such modifications, additions, and substitutions fallwithin the scope of the present invention, which is best defined by theclaims appended below.

What is claimed is:
 1. An exposure apparatus that exposes an object withan energy beam via a projection optical system, the apparatuscomprising: a stage having a holder that holds the object; an encodersystem in which one of a grating section and a head is provided at thestage, and which measures positional information of the stage by aplurality of the heads that face the grating section; a drive systemhaving a motor to drive the stage, that drives the stage by the motor sothat the object is moved in directions of six degrees of freedomincluding a first direction, a second direction and a third direction,the first direction and the second direction being orthogonal within apredetermined plane perpendicular to an optical axis of the projectionoptical system and the third direction being orthogonal to the first andthe second directions; and a controller coupled to the encoder systemand the drive system, that controls the drive system based onmeasurement information of the encoder system while compensating for ameasurement error of the encoder system that occurs due to a differencein position in the third direction between a reference plane with whichthe object substantially coincides at a time of the exposure and thegrating section, wherein during driving of the stage, the controllerswitches one head of the plurality of heads to another head, and afterthe switching, controls the drive system using the positionalinformation measured by the another head.
 2. The exposure apparatusaccording to claim 1, wherein the reference plane is an image plane ofthe projection optical system.
 3. The exposure apparatus according toclaim 1, wherein the controller decides the positional information to bemeasured by the another head based on the positional informationmeasured by the head used before the switching, and after the switching,the measurement by the another head is performed using the positionalinformation that has been decided.
 4. The exposure apparatus accordingto claim 3, wherein the positional information to be measured by theanother head is decided so that a position of the stage is maintainedbefore and after the switching or so that positional information of thestage continuously links before and the after the switching.
 5. Theexposure apparatus according to claim 3, wherein the encoder systemmeasures positional information of the stage in at least directions ofthree degrees of freedom that include a direction parallel to thepredetermined plane, before and after the switching each, themeasurement by three or four heads that face the grating section isperformed, and during driving of the stage, the number of heads thatface the grating section is changed from one of three and four to theother.
 6. The exposure apparatus according to claim 3, wherein in orderto decide the positional information to be measured by the another head,positional information of the stage in a different direction that isdifferent from a direction parallel to the predetermined plane is used.7. The exposure apparatus according to claim 6, wherein the differentdirection includes a rotational direction within the predeterminedplane.
 8. The exposure apparatus according to claim 3, wherein thepositional information to be measured by the another head is decidedwhile a head used before the switching and a head to be used after theswitching both face the grating section.
 9. The exposure apparatusaccording to claim 3, wherein the switching is performed while a headused before the switching and a head to be used after the switching bothface the grating section.
 10. The exposure apparatus according to claim3, wherein the positional information to be measured by the another headis decided at a time of the switching.
 11. The exposure apparatusaccording to claim 3, wherein before the switching the measurement bythree of the heads that face the grating section is performed, and bythe switching the measurement by three heads is performed, the threeheads including the another head that is different from the three of theheads used before the switching.
 12. The exposure apparatus according toclaim 3, wherein the grating section includes four scales on each ofwhich a grating is formed, before the switching, the measurement byheads that face at least three of the four scales is performed, andbased on the positional information measured by the at least threeheads, the positional information to be measured by the another headthat is different from the at least three heads is decided.
 13. Theexposure apparatus according to claim 3, wherein the positionalinformation that has been decided is set as an initial value in theanother head.
 14. The exposure apparatus according to claim 3, whereinthe stage is provided with the plurality of heads, and is moved underthe grating section in the exposure.
 15. The exposure apparatusaccording to claim 3, wherein the controller compensates for ameasurement error of the encoder system that occurs due to at least oneof the grating section and the head.
 16. The exposure apparatusaccording to claim 15, wherein the controller compensates for ameasurement error of the encoder system that occurs due to at least oneof displacement and an optical property of the head.
 17. The exposureapparatus according to claim 15, wherein the controller compensates fora measurement error of the encoder system that occurs due to at leastone of flatness and a formation error of the grating section.
 18. Theexposure apparatus according to claim 3, wherein the controllercompensates for a measurement error of the encoder system that occursdue to inclination or rotation of the stage.
 19. The exposure apparatusaccording to claim 3, wherein the controller compensates for ameasurement error of the encoder system related to a measurementdirection of the positional information that occurs due to a position ofthe stage in a direction different from the measurement direction. 20.The exposure apparatus according to claim 3, wherein the controllercorrects the measurement information of the encoder system or a targetposition at which the object is positioned so that the measurement erroris compensated for.
 21. The exposure apparatus according to claim 3,wherein the object is exposed with the energy beam via a mask, and in anoperation of the exposure, a position of the mask is controlled so thatthe measurement error is compensated for, while the drive system iscontrolled based on the measurement information of the encoder system.22. The exposure apparatus according to claim 3, further comprising: anozzle unit provided surrounding a lower end portion of the projectionoptical system, that forms a liquid immersion area with a liquid underthe projection optical system, wherein the other of the grating sectionand the plurality of heads is provided on an outer side of the nozzleunit with respect to the projection optical system, and the object isexposed with the energy beam via the projection optical system and theliquid of the liquid immersion area.
 23. A device manufacturing method,including exposing a substrate using the exposure apparatus according toclaim 1; and developing the substrate that has been exposed.
 24. Anexposure method of exposing an object with an energy beam via aprojection optical system, the method comprising: in an encoder systemin which one of a grating section and a head is provided at a stage thatholds the object, by a plurality of the heads that face the gratingsection, measuring positional information of the stage; controlling,based on measurement information of the encoder system, a drive systemthat is capable of driving the stage so that the object is moved indirections of six degrees of freedom including a first direction, asecond direction and a third direction, while compensating for ameasurement error of the encoder system that occurs due to a differencein position in the third direction between a reference plane with whichthe object substantially coincides at a time of the exposure and thegrating section, the first direction and the second direction beingorthogonal within a predetermined plane perpendicular to an optical axisof the projection optical system and the third direction beingorthogonal to the first and the second directions; and switching onehead of the plurality of heads to another head during driving of thestage, wherein after the switching, the positional information measuredby the another head is used for control of the drive system.
 25. Theexposure method according to claim 24, wherein the reference plane is animage plane of the projection optical system.
 26. The exposure methodaccording to claim 24, wherein the positional information to be measuredby the another head is decided based on the positional informationmeasured by the head used before the switching, and after the switching,the measurement by the another head is performed using the positionalinformation that has been decided.
 27. The exposure method according toclaim 26, wherein the positional information to be measured by theanother head is decided so that a position of the stage is maintainedbefore and after the switching or so that positional information of thestage continuously links before and the after the switching.
 28. Theexposure method according to claim 26, wherein positional information ofthe stage in at least directions of three degrees of freedom thatinclude a direction parallel to the predetermined plane is measured bythe encoder system, before and after the switching each, the measurementby three or four heads that face the grating section is performed, andduring driving of the stage, the number of heads that face the gratingsection is changed from one of three and four to the other.
 29. Theexposure method according to claim 26, wherein in order to decide thepositional information to be measured by the another head, positionalinformation of the stage in a different direction that is different froma direction parallel to the predetermined plane is used.
 30. Theexposure method according to claim 29, wherein the different directionincludes a rotational direction within the predetermined plane.
 31. Theexposure method according to claim 26, wherein the positionalinformation to be measured by the another head is decided while a headused before the switching and a head to be used after the switching bothface the grating section.
 32. The exposure method according to claim 26,wherein the switching is performed while a head used before theswitching and a head to be used after the switching both face thegrating section.
 33. The exposure method according to claim 26, whereinthe positional information to be measured by the another head is decidedat a time of the switching.
 34. The exposure method according to claim26, wherein before the switching the measurement by three of the headsthat face the grating section is performed, and by the switching themeasurement by three heads is performed, the three heads including theanother head that is different from the three of the heads used beforethe switching.
 35. The exposure method according to claim 26, whereinthe grating section includes four scales on each of which a grating isformed, before the switching, the measurement by heads that face atleast three of the four scales is performed, and based on the positionalinformation measured by the at least three heads, the positionalinformation to be measured by the another head that is different fromthe at least three heads is decided.
 36. The exposure method accordingto claim 26, wherein the positional information that has been decided isset as an initial value in the another head.
 37. The exposure methodaccording to claim 26, wherein the stage is provided with the pluralityof heads, and is moved under the grating section in the exposure. 38.The exposure method according to claim 26, wherein during driving of thestage, a measurement error of the encoder system that occurs due to atleast one of the grating section and the head is compensated for. 39.The exposure method according to claim 38, wherein a measurement errorof the encoder system that occurs due to at least one of displacementand an optical property of the head is compensated for.
 40. The exposuremethod according to claim 38, wherein a measurement error of the encodersystem that occurs due to at least one of flatness and a formation errorof the grating section is compensated for.
 41. The exposure methodaccording to claim 26, wherein during driving of the stage, ameasurement error of the encoder system that occurs due to inclinationor rotation of the stage is compensated for.
 42. The exposure methodaccording to claim 26, wherein during driving of the stage, ameasurement error of the encoder system related to a measurementdirection of the positional information that occurs due to a position ofthe stage in a direction different from the measurement direction iscompensated for.
 43. The exposure method according to claim 26, whereinduring driving of the stage, the measurement information of the encodersystem or a target position at which the object is positioned iscorrected so that the measurement error is compensated for.
 44. Theexposure method according to claim 26, wherein the object is exposedwith the energy beam via a mask, and in an operation of the exposure, aposition of the mask is controlled so that the measurement error iscompensated for, while the drive system system is controlled based onthe measurement information of the encoder system.
 45. The exposuremethod according to claim 26, wherein a liquid immersion area isfoliated with a liquid under the projection optical system by a nozzleunit provided surrounding a lower end portion of the projection opticalsystem, and the object is exposed with the energy beam via theprojection optical system and the liquid of the liquid immersion area,and the other of the grating section and the plurality of heads isprovided on an outer side of the nozzle unit with respect to theprojection optical system.
 46. A device manufacturing method, includingexposing a substrate using the exposure method according to claim 24;and developing the substrate that has been exposed.
 47. A method ofmaking an exposure apparatus that exposes an object with an energy beamvia a projection optical system, the method comprising: providing astage having a holder that holds the object; providing an encoder systemin which one of a grating section and a head is provided at the stage,and which measures positional information of the stage by a plurality ofthe heads that face the grating section; providing a drive system havinga motor to drive the stage, that drives the stage by the motor so thatthe object is moved in directions of six degrees of freedom including afirst direction, a second direction and a third direction, the firstdirection and the second direction being orthogonal within apredetermined plane perpendicular to an optical axis of the projectionoptical system and the third direction being orthogonal to the first andthe second directions; and coupling a controller to the encoder systemand the drive system, the controller controlling the drive system basedon measurement information of the encoder system while compensating fora measurement error of the encoder system that occurs due to adifference in position in the third direction between a reference planewith which the object substantially coincides at a time of the exposureand the grating section, wherein during driving of the stage, thecontroller switches one head of the plurality of heads to another head,and after the switching, controls the drive system using the positionalinformation measured by the another head.